To support both CW and CM, return alarmurl from policy ref

To support both CW and CM, return alarmurl from policy ref

This is so we can still have the following:
  AlarmActions:
  - {Ref: ServerScaleUpPolicy}

and use Ceilometer underneath.

The watchrule now tries to look up the resource by
both name and resource_by_refid.

Change-Id: I4759806919ab4f3ccef66698235b23f7f310cb03