s3-messaging: use messaging_ctdbd_reinit() in messaging_reinit()

s3-messaging: use messaging_ctdbd_reinit() in messaging_reinit()

This is the last step to fix a regression introduced by

  3fe3226daa8488e0fa787c40359c3401b6f05fc0 and
  3fe3226daa8488e0fa787c40359c3401b6f05fc0^

where we pass the ctdb-messaging object conn to db_open() and add a
reference to it to the private db_ctdb_ctx for later use. Unfortunately
reinit_after_fork() destroys conn, leaving us with an invalid reference.

The previous patches added new lower level functions
messaging_ctdbd_reinit() and ctdbd_reinit_connection(), finally use them
them from messaging_reinit(). They preserve the conn object and simply
reinitialize the IPC fd.

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
Autobuild-User(master): Ralph Böhme <slow@samba.org>
Autobuild-Date(master): Mon Jul 11 23:45:20 CEST 2016 on sn-devel-144