Deduplicate status call checks

This commit updates the jsonschema validation method validate_response()
to use the rest client method expected_success() to check that the
correct status code response is received. Previously validate response
was doing the same check despite there already being a method available
for doing the check. As a part of using expected_success() to validate
the status codes using the jsonschema it was necessary to expand
expected_successs() to handle both single expected codes as well as a
list of codes. This is because it's perfectly valid for the jsonschema
to specify a list of expected responses.

Change-Id: I400bb9aff89c18f3964a1d8ec45bfb8dfd75301d
Merge "Deduplicate status call checks"