ctdb-locking: Set real-time priority for lock helpers

To avoid lock helper starvation when userspace robust mutexes are
enabled.

Commit 6f072f85a1 removed reset_scheduler(),
to avoid resetting scheduler priority.  However, that is not sufficient
because of commit 1be8564e55, which sets
SCHED_RESET_ON_FORK flag.  With SCHED_RESET_ON_FORK, all CTDB child
processes will automatically have normal scheduling priority.

Signed-off-by: Amitay Isaacs <amitay@gmail.com>
Reviewed-by: Martin Schwenke <martin@meltin.net>

Autobuild-User(master): Martin Schwenke <martins@samba.org>
Autobuild-Date(master): Thu Sep 11 11:31:10 CEST 2014 on sn-devel-104

ctdb/server/ctdb_lock_helper.c

@@ -123,6 +123,8 @@ int main(int argc, char *argv[])
 		exit(1);
 	}
 
+	set_scheduler();
+
 	ppid = atoi(argv[1]);
 	write_fd = atoi(argv[2]);
 	lock_type = argv[3];