Add Mock for get_vapp_metadata

It's the same API method for vApps and VMs, so need to check both IDs.

This only returns a piece of custom metadata, not the system metadata that is also returned.

This commit also adds metadata to be retrived by this method from the Mock data.
Add Mock for put metadata
Add Mock for get_vms_in_lease_from_query

The only option implemented here is a filter by href as that is all we need for our tests. It can easily be extended as required.