vdsm-tool usage: Adding path variable to init script

Change-Id: Ia5c07ee9bdc99a5b6d491e2ca2be99d3cf04c73f
Signed-off-by: Yaniv Bronhaim <ybronhei@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/16549
Reviewed-by: Dan Kenigsberg <danken@redhat.com>