core: Adding context ctor to UpgradeOvirtNodeInternalCommand

I still fail to understand why not add to all commands.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1120720
Change-Id: I0555fd221f1fd3dfd8c4dbd35e5cc0fc919b3906
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>