Rename functions in nova.compute.flavors from instance_type

Second step in removing references to instance_types. Remove all
references to instance_type in nova.compute.flavors.
Also update compute devref to reflect changed name.
Partially implements bp flavor-instance-type-dedup

renamed:  nova/tests/test_instance_types.py -> test_flavors.py

Change-Id: I7413bf832c61d04ab90ec8b1370d3f01372c4172
Merge "Rename functions in nova.compute.flavors from instance_type"