Wait for memory and vcpus from hypervisor stats

Building on what was added in I43d72cc0d2c1ded70af28d9861aa6e28838795bf,
this makes use of the new memory and vcpu parameters in
wait_for_hypervisor_stats to make sure that the script checks the
correct memory amount and vcpu count are available.

Change-Id: I40ac243a5c9d97264accbefe4ce96497914b6b01
Merge "Wait for memory and vcpus from hypervisor stats"