Hide the flavor selection if we don't do flavor matching

Both the Flavor panel and the possibility to choose flavor when
editing roles is hidden when flavor matching is not done.
Flavor matching is disabled by adding DEPLOYMENT_ROLE = 'poc'
into local_settings.py. See also https://review.openstack.org/#/c/124586/

Change-Id: I055769f59b5321dd4c4a27877d5f3485cb4106bd
Merge "Hide the flavor selection if we don't do flavor matching"