ctdb: Print locks latency in machinereadable stats

ctdb: Print locks latency in machinereadable stats

Bug: https://bugzilla.samba.org/show_bug.cgi?id=13742
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Martin Schwenke <martin@meltin.net>
Autobuild-User(master): Volker Lendecke <vl@samba.org>
Autobuild-Date(master): Wed Jan 16 05:34:17 CET 2019 on sn-devel-144

(cherry picked from commit 193a0d6f01372604b925d1972591062a0bb2400f)

Autobuild-User(v4-10-test): Karolin Seeger <kseeger@samba.org>
Autobuild-Date(v4-10-test): Mon Feb  4 13:09:49 CET 2019 on sn-devel-144