1. add lbaas l7 switching clients
2. enhance to delete l7 resources if present
3. enhance NSX-v scenario to support l7 switching testing
3.1 check floatingip assiged to server before ping test
NSX-v3 can take 500+ second to assign floatingip to VM
3.2 enhance test_lbaas_round_robin to support l7 test
3.3 test_lbaas_l7_switching_ops only test URL starts_with
validation.
4. l7_switching_ops requires around 2000 seconds. When run test
set OS_TEST_TIMEOUT=2400 to avoid fixture timeout.
5. add CONF.nsxv.bugs_to_resolve to skip tests that can not be
run at sepcific NSX plugin environment.
6. doc/README-LBaaS.rst describes limitation and how to run
tests at different plugin's and backends.
Change-Id: Ib2ee4ce57d45882d76e25ce7b7bba3d825bf34ab
2065418288