core: Using signed password for ovirt-node provisioning

Using MD5 signature util.

Change-Id: I82d9e0f368e3b6e36098b33863ff7998f789688b
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1109540
Signed-off-by: Yaniv Bronhaim <ybronhei@redhat.com>