port test_aggregates and test_hosts into nova v3 part2

this port test_aggregates and test_hosts into nova v3,
and port the corresponding client aggregate_client and
host_client.

Partially implements blueprint nova-v3-api-tests

Change-Id: I0f7b4f548f68b634258bb396bd3d245b02561e3a
Merge "port test_aggregates and test_hosts into nova v3 part2"