increase heat guests

heat is booting a real fedora, which makes m1.tiny completely not
appropriate. We want to limit disk io, so boot as a 2 vcpu 1G guest
to try to get some better performance out of these guests when
tested in tempest.

Change-Id: I80de67080a5106c2d8921e146c37c614ee5f8abf
Merge "increase heat guests"