Remove default flavor from every template

With the push to using the new setup-flavors provided by
os-cloud-config, the default flavor will no longer be called
'baremetal', and Heat will always validate the default even if it
is overridden. To that end, remove the default flavor from every
flavor definition. Just to be certain, also add a custom_constraint
to every flavor definition that was missing it.

Change-Id: I24251e73be4e86738857f73b89499f592c4908de
Merge "Remove default flavor from every template"