baremetal: set capabilites explicitly

ComputeDriver, base class of compute drivers, has dict capabilities
to show if the compute driver implements some functions. Compute
manger will check this with capabilities['has_imagecache'] or
capabilities['supports_recreate'] directly. If use compute driver
baremetal, there is code path leading KeyError. Let set capabilites
explicitly to avoid this.

Partial-Bug: #1261636

Change-Id: I5097d271df0d6ad419f530787d890288163d06c5
Merge "baremetal: set capabilites explicitly"