handle termination of syncrepl watcher thread
In some cases, the thread could have been already terminated and
sending a signal to the thread using pthread_kill() would result in an
error. Now if the thread has already been terminated for some reason,
only an error message is logged.
https://fedorahosted.org/bind-dyndb-ldap/ticket/149
Reviewed-By: Petr Spacek <pspacek@redhat.com>
Reviewed-By: Thierry Bordaz <tbordaz@redhat.com>