vdsm-tool: fix qemu-sanlock configuration

Fixing the logic about qemu-sanlock configuration: if sanlock is
enabled then qemu-sanlock.conf needs to be updated.

Change-Id: I3d2a6b05fb8fbf0ef2e9599fd1a740a7091680d4
Signed-off-by: Federico Simoncelli <fsimonce@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/19094
Reviewed-by: Eyal Edri <eedri@redhat.com>
Tested-by: Eyal Edri <eedri@redhat.com>
Reviewed-by: Allon Mureinik <amureini@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>