xenapi: Add cleanup_sm_locks script

XenServer 5.6 and 6.0 don't appear to be cleaning up sm locks when using
a FileSR. When enough locks accumulate, this causes image related
operations to fail.

This cleanup script is a stop-gap solution that can be run against all
of the dom0's in the cluster to prevent too many locks from
accumulating.

We can remove this script when the root-cause is fixed upstream.

References 1103158

Change-Id: I798bcfeb727a59003910b82d331fdbe031c4a2b4
Merge "xenapi: Add cleanup_sm_locks script"