oVirt Node Upgrade: Support N configuration

To have multiple configurations supported for node upgrade and same code
for upstream/downstream, this patch will include the delimiter ":" to the below
elements in vdc_options.
- OvirtInitialSupportedIsoVersion
- oVirtISOsRepositoryPath
- OvirtIsoPrefix

Additionally:
- OvirtIsoPrefix now includes prefix and regex to list ISOs.
- Includes OvirtNodeOS to regex node OS
- New class OVirtNodeInfo to hold informations about upgrade.

Change-Id: Ibfb9dc5d0dc8780b519107acbe0ae866831f782c
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=979231
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>