Remove _report_driver_status from compute/manager.py

After the blueprint no-compute-fanout-to-scheduler, there is no
need for nova compute to fanout its capabilities to nova scheduler,
so we can remove _report_driver_status as it is no use now.

Change-Id: I749204d7d6461993d0c42bf5877b65c5ec17c62f
Merge "Remove _report_driver_status from compute/manager.py"