ctdb-scripts: Initialise CTDB_NFS_CALLOUT in statd-callout

ctdb-scripts: Initialise CTDB_NFS_CALLOUT in statd-callout

Some configurations may set CTDB_NFS_CALLOUT to the empty string.
They may do this if they allow a choice of NFS implementations.  In
this case the default call-out for Linux kernel NFS should be used.
However, statd-callout does not call nfs_callout_init() to set the
default.  Therefore, statd-callout is unable to restart the lock
manager, so the grace period is never entered.

statd-callout must call nfs_callout_init() before trying to restart
the lock manager.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=12589

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>
Autobuild-User(master): Martin Schwenke <martins@samba.org>
Autobuild-Date(master): Thu Feb 16 09:21:03 CET 2017 on sn-devel-144

(cherry picked from commit 5e7ae1b1e2fa8137aaa6a2a2f446156ae61f4c84)

Autobuild-User(v4-4-test): Karolin Seeger <kseeger@samba.org>
Autobuild-Date(v4-4-test): Fri Feb 17 16:02:00 CET 2017 on sn-devel-144