daemon: Support per-node robust mutex feature

daemon: Support per-node robust mutex feature

To enable TDB mutex support, set tunable TDBMutexEnabled=1.

When databases are attached for the first time, attach flags must include
TDB_MUTEX_LOCKING and TDBMutexEnabled must set to enable mutex support.

However, when CTDB attaches databases internally for recovery, it will
enable mutex support if TDBMutexEnabled is set.

Signed-off-by: Amitay Isaacs <amitay@gmail.com>
Reviewed-by: Stefan Metzmacher <metze@samba.org>
Autobuild-User(master): Amitay Isaacs <amitay@samba.org>
Autobuild-Date(master): Wed Jul  9 06:45:17 CEST 2014 on sn-devel-104

(Imported from commit 55fbe364b93000c7766e95e16fa35cc6a80c697b)