Create flavor from heat context

Create flavor from heat context

JIRA: YARDSTICK-582

Create a customizable flavor via heat context. All heat parameters
are configurable including Core Affinity. The default flavor name
is XXXX-flavor where XXXX is stackname. Flavor attributes are taken
from the heat context file. If a flavor attribute is not used it
takes default attribute value. If flavor name is not specified it
uses the server name + "-flavor" or stack-name + "-flavor".

Compute node specific attributes are configurable via "extra_specs"
attribute. See
https://docs.openstack.org/admin-guide/compute-flavors.html for
details.

Change-Id: If4015970b889b0b95bfa8eba9491ebf31e92f2c7
Signed-off-by: DanielMartinBuckley <daniel.m.buckley@intel.com>