selftests: Convert "net ads dns async" test to python

selftests: Convert "net ads dns async" test to python

The current test uses the dig tool from bind9 but this tool has been
rewritten in 9.17.7 to use bind's netmgr functions instead of isc_socket
(commit 94b7988efb0f9b96415dd2966e6070450d960263).

The problem is that these 'netmgr' functions use libuv internally, and, on
systems supporting it, they end up using the sendmmsg() syscall which is not
catched by socket wrapper so the test fails.

This commit converts the test to python and uses the dnspython module
instead of the dig tool. Backtraces follow as reference.

Backtrace from dig v9.16.28 (working):

 #0  0x00007ffff778edee in sendmsg () from /lib64/libc.so.6
 #1  0x00000000005e5dee in cmsgsend (s=s@entry=12, level=level@entry=0, type=type@entry=1, res=<optimized out>) at net.c:515
 #2  0x00000000005e616c in try_dscp_v4 () at net.c:623
 #3  try_dscp () at net.c:696
 #4  0x00007ffff7708ad7 in __pthread_once_slow () from /lib64/libc.so.6
 #5  0x00000000005e66d7 in initialize_dscp () at net.c:702
 #6  isc_net_probedscp () at net.c:707
 #7  0x00000000005e8460 in socket_create (manager=0x6b49c0, pf=2, type=<optimized out>, socketp=0x7ffff0012b00, dup_socket=0x0) at socket.c:2454
 #8  0x000000000043cfcd in send_udp (query=0x7ffff00129a8) at dighost.c:2897
 #9  0x000000000043f9c7 in onrun_callback (task=<optimized out>, event=<optimized out>) at dighost.c:4271
 #10 0x00000000005dfefe in task_run (task=0x6b5c70) at task.c:851
 #11 isc_task_run (task=0x6b5c70) at task.c:944
 #12 0x00000000005ca0ce in isc__nm_async_task (worker=0x6b8970, ev0=0x716250) at netmgr.c:873
 #13 process_netievent (worker=worker@entry=0x6b8970, ievent=0x716250) at netmgr.c:952
 #14 0x00000000005ca2ba in process_queue (worker=worker@entry=0x6b8970, type=type@entry=NETIEVENT_TASK) at netmgr.c:1021
 #15 0x00000000005caa43 in process_all_queues (worker=0x6b8970) at netmgr.c:792
 #16 async_cb (handle=0x6b8cd0) at netmgr.c:821
 #17 0x00007ffff7898a4d in ?? () from /lib64/libuv.so.1
 #18 0x00007ffff78b4217 in ?? () from /lib64/libuv.so.1
 #19 0x00007ffff789e40a in uv_run () from /lib64/libuv.so.1
 #20 0x00000000005ca31e in nm_thread (worker0=0x6b8970) at netmgr.c:727
 #21 0x00000000005e2315 in isc__trampoline_run (arg=0x6b7c40) at trampoline.c:198
 #22 0x00007ffff7703767 in start_thread () from /lib64/libc.so.6
 #23 0x00007ffff778dc10 in clone3 () from /lib64/libc.so.6

Backtrace from dig v9.17.7 (not working):

 #0  0x00007ffff7684480 in syscall () from /lib64/libc.so.6
 #1  0x00007ffff754aed0 in uv__sendmmsg (vlen=0, mmsg=0x0, fd=10) at src/unix/linux-syscalls.c:163
 #2  uv__udp_mmsg_init () at src/unix/udp.c:74
 #3  0x00007ffff7606ad7 in __pthread_once_slow () from /lib64/libc.so.6
 #4  0x00007ffff7541bd9 in uv_once (guard=<optimized out>, callback=<optimized out>) at src/unix/thread.c:440
 #5  0x00007ffff7539e9b in uv__udp_sendmsg (handle=0x7ffff50535b8) at src/unix/udp.c:415
 #6  uv__udp_send (send_cb=0x7ffff7a41db0 <udp_send_cb>, addrlen=<optimized out>, addr=<optimized out>, nbufs=1, bufs=0x7ffff506c720, handle=0x7ffff50535b8, req=0x7ffff506c878) at src/unix/udp.c:773
 #7  uv_udp_send (req=req@entry=0x7ffff506c878, handle=handle@entry=0x7ffff50535b8, bufs=bufs@entry=0x7ffff506c720, nbufs=nbufs@entry=1, addr=<optimized out>, send_cb=send_cb@entry=0x7ffff7a41db0 <udp_send_cb>) at src/uv-common.c:464
 #8  0x00007ffff7a42308 in udp_send_direct (peer=0x7ffff5dfa988, req=0x7ffff506c700, sock=0x7ffff5053000) at netmgr/udp.c:839
 #9  isc__nm_async_udpsend (worker=<optimized out>, ev0=0x7ffff5dfa950) at netmgr/udp.c:780
 #10 0x00007ffff7a47de7 in isc__nm_udp_send (handle=<optimized out>, region=0x7ffff5dfaa90, cb=0x555555566250 <send_done>, cbarg=<optimized out>) at netmgr/udp.c:749
 #11 0x0000555555562ac2 in send_udp (query=0x7ffff502a000) at /usr/src/debug/bind-9.18.2-1.1.x86_64/bin/dig/dighost.c:2899
 #12 udp_ready (handle=0x7ffff5026180, eresult=ISC_R_SUCCESS, arg=<optimized out>) at /usr/src/debug/bind-9.18.2-1.1.x86_64/bin/dig/dighost.c:2974
 #13 0x00007ffff7a37d34 in isc__nm_async_connectcb (worker=worker@entry=0x7ffff622f000, ev0=ev0@entry=0x7ffff5026480) at netmgr/netmgr.c:2704
 #14 0x00007ffff7a3ca20 in process_netievent (worker=worker@entry=0x7ffff622f000, ievent=0x7ffff5026480) at netmgr/netmgr.c:940
 #15 0x00007ffff7a3d027 in process_queue (worker=worker@entry=0x7ffff622f000, type=type@entry=NETIEVENT_NORMAL) at netmgr/netmgr.c:977
 #16 0x00007ffff7a3d203 in process_all_queues (worker=0x7ffff622f000) at netmgr/netmgr.c:733
 #17 async_cb (handle=0x7ffff622f360) at netmgr/netmgr.c:762
 #18 0x00007ffff7531a4d in uv__async_io (loop=0x7ffff622f010, w=<optimized out>, events=<optimized out>) at src/unix/async.c:163
 #19 0x00007ffff754d217 in uv__io_poll (loop=0x7ffff622f010, timeout=<optimized out>) at src/unix/epoll.c:374
 #20 0x00007ffff753740a in uv__io_poll (timeout=<optimized out>, loop=0x7ffff622f010) at src/unix/udp.c:122
 #21 uv_run (loop=loop@entry=0x7ffff622f010, mode=mode@entry=UV_RUN_DEFAULT) at src/unix/core.c:391
 #22 0x00007ffff7a3d624 in nm_thread (worker0=0x7ffff622f000) at netmgr/netmgr.c:664
 #23 0x00007ffff7a6c915 in isc__trampoline_run (arg=0x555555599210) at /usr/src/debug/bind-9.18.2-1.1.x86_64/lib/isc/trampoline.c:187
 #24 0x00007ffff7601767 in start_thread () from /lib64/libc.so.6
 #25 0x00007ffff768bc10 in clone3 () from /lib64/libc.so.6

Signed-off-by: Samuel Cabrero <scabrero@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Sat Jun  4 00:27:29 UTC 2022 on sn-devel-184