compute: virt: Fix Instance creation

Instance is a namedtuple defined in ceilometer/compute/virt/inspector.py. Its
fields are 'name' and 'UUID'. Therefore, the 'uuid' field used in
inspect_instances should be 'UUID'.

Change-Id: I844b457bc75603d6325bfe3eb239012cec12c6b9
Merge "compute: virt: Fix Instance creation"