node: Determine ovirt-node-plugin-vdsm version

Determine version of ovirt-node-plugin-vdsm as a part of node detection.

Bug-Url: https://bugzilla.redhat.com/1079821
Change-Id: Icfa4fb729cb2db3fba9076a1184d2906cee06868
Signed-off-by: Martin Perina <mperina@redhat.com>