port some servers tests into nova v3 part2

this ports test_servers, test_create_server and test_multiple_create
into nova v3 api, and also ports corresponding client.

Partially implements blueprint nova-v3-api-tests

Change-Id: Icc2de969a415ef2e2cb85a409b6cdcc47c908322
Merge "port some servers tests into nova v3 part2"