Add a new microversion to change the flavor field in the server
details to display a subset of the flavor information instead of
just a link to the original flavor.
This is more reliable since it shows the actual instance size, while
the flavor may have been deleted/recreated in the meantime or the
flavor extra-specs may have been modified.
Implements: blueprint instance-flavor-api
Change-Id: If646149efb7eec8c90bf7d07c39ff4c495349941