s3: Fix smb2 handling error returns from aio

s3: Fix smb2 handling error returns from aio

Found when reading with aio_fork beyond the end of file.

Metze, Jeremy, please check!

Without this we get

[2011/08/02 21:02:54.082661,  0] lib/util.c:778(smb_panic_s3)
  PANIC (pid 2302): smbd/smb2_read.c:593: Type mismatch: name[NULL] expected[struct smbd_smb2_read_state]
[2011/08/02 21:02:54.094316,  0] lib/util.c:882(log_stack_trace)
  BACKTRACE: 23 stack frames:
   #0 bin/smbd(log_stack_trace+0x2d) [0xb72873d8]
   #1 bin/smbd(smb_panic_s3+0x7c) [0xb7287529]
   #2 bin/smbd(smb_panic+0x2f) [0xb7277e1f]
   #3 /root/git/s3-work/source3/bin/libtalloc.so.2 [0xb6c6bc48]
   #4 /root/git/s3-work/source3/bin/libtalloc.so.2 [0xb6c6ec79]
   #5 /root/git/s3-work/source3/bin/libtalloc.so.2(_talloc_get_type_abort+0x34) [0xb6c6ecb3]
   #6 bin/smbd [0xb6fbc405]
   #7 bin/smbd(_tevent_req_notify_callback+0x4a) [0xb729a85a]
   #8 bin/smbd [0xb729a888]
   #9 bin/smbd(_tevent_req_done+0x19) [0xb729aa73]
   #10 bin/smbd [0xb6fae517]
   #11 bin/smbd [0xb6fad258]
   #12 bin/smbd(smbd_aio_complete_aio_ex+0xf5) [0xb6fad6e8]
   #13 /root/git/inst/modules/vfs/aio_fork.so [0xb66d4992]
   #14 bin/smbd(run_events_poll+0x400) [0xb7297df2]
   #15 bin/smbd(smbd_process+0xd75) [0xb6f9d3a7]
   #16 bin/smbd [0xb756f07b]
   #17 bin/smbd(run_events_poll+0x400) [0xb7297df2]
   #18 bin/smbd [0xb7298254]
   #19 bin/smbd(_tevent_loop_once+0x9e) [0xb72986ac]
   #20 bin/smbd(main+0x185c) [0xb7570e59]
   #21 /lib/i686/cmov/libc.so.6(__libc_start_main+0xe5) [0xb6b08455]
   #22 bin/smbd [0xb6f14e01]

Autobuild-User: Volker Lendecke <vlendec@samba.org>
Autobuild-Date: Tue Aug  2 22:33:15 CEST 2011 on sn-devel-104