Automatic merge from submit-queue

Add `clusterid`, an optional parameter to storageclass.

At present, admin doesn't have the privilege to chose the
trusted storage pool from which persistent gluster volume
has to be provided.

This patch introduce a new storage class parameter which allows
the admin to specify storage pool/cluster if required.
Signed-off-by: Humble Chirammal <hchiramm@redhat.com>