CP 2.0: implement async endpoint for virt-who hypervisors checkin
CP 2.0 supports an async endpoint for hypervisor checkin. If the api does not exist, as in current CP, then it falls back to synchronous checkin.
Katello will need to be changed to:
1) add pass-through async endpoint
2) begin polling the task itself to catch the new/changed hypervisors
3) be sure to handle facts on the created hypervisors since the async endpoint now supports them