Fixing up the connection_type determining logic.

Since the gridcentric manager already has a reference to the
compute manager, we can just query what compute driver it has
picked for itself and build our vms connectoin off of that. This
ensures that we are using the same driver as nova-compute.

Change-Id: I9f2402f87248ef298fc9c67d34cdd97a3de39921
Merge "Fixing up the connection_type determining logic." into stable/folsom