audit: make sure we never skip the multicast broadcast

When the auditd connection is reset, either intentionally or due to
a failure, any records that were in the main backlog queue would not
be sent in a multicast broadcast.  This patch fixes this problem by
not flushing the main backlog queue on a connection reset, the main
kauditd_thread() will take care of that normally.

Resolves: https://github.com/linux-audit/audit-kernel/issues/41
Reviewed-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>