Fix memory leak in share mode locking.

Fix memory leak in share mode locking.

Not freeing up(and reparenting to NULL context) ndr buffer
used for TDB updates resulting in huge memory leak when there
in high volume of opens and closes happening on same object.

Free the buffer before reparenting its parent to NULL context.

https://bugzilla.samba.org/show_bug.cgi?id=11934

Signed-off-by: Hemanth Thummala <hemanth.thummala@nutanix.com>
Signed-off-by: Saji VR <saji.vr@nutanix.com>
Reviewed-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
Autobuild-User(master): Volker Lendecke <vl@samba.org>
Autobuild-Date(master): Fri May 27 18:43:31 CEST 2016 on sn-devel-144