vdsm: support latest VDSM API connection changes

vdsClient has changed the API for connecting to
the daemon with the following patch:
http://gerrit.ovirt.org/#/c/16225/2

Adding support for the new API
keeping compatibility with previous version.

Change-Id: I1f08dc344d8dd1c46de79fbd746b9d89d89b70d6
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>