hsm: remove obsolete getVolumePath verb

We can remove the getVolumePath verb as it was never officially in use.

Change-Id: I7d15dee9e805478f4b4d2bfcb7985484db77339e
Signed-off-by: Federico Simoncelli <fsimonce@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/33353
Reviewed-by: Nir Soffer <nsoffer@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>