Add metadata option to Nova Create API Wrapper

The Nova Create API Wrapper doesn't pass through
the metadata variable, requring any dashboards
that spin up VMs with metadata to use the python
libraries directly.

Closes-Bug: 1347824

Change-Id: Ib4cb98e1c510466edc7558697f9d015e80b882ab
Merge "Add metadata option to Nova Create API Wrapper"