Include 207 in http success status code RFC-4918

This patch extend the http success status code with 207.
207 status code is introduced in RFC 4918.

Some API like - Nova 'os-server-external-events' return '207'
status code in case some event are accepted out of multiple event.
To support those return code in tempest, expected_success() needs to
be extended to include '207' as success status code.

Change-Id: I0ca0c80c466b1e97873d404c575af5b4a9be07a6
Adds method to verify multiple tenants are available

Based on is_multi_user()

Change-Id: Ifeceb3244a87c378e70f387dde1d22bc20c9f612
Allow some lag for floating IP to reach a status

The current test checks the floating IP status as soon as possible
without allowing the status to converge.  This doesn't allow for the
fact that implementations don't report the new status until after
connectivity has been torn down.  There may be some expected lag that
is not allowed by the current test.

Change-Id: Icfe4bb2c40fde540bc2a6371630aa3f12dd945ff
Closes-Bug: #1381617
Merge "Allow some lag for floating IP to reach a status"
Merge "Adds method to verify multiple tenants are available"
Merge "Include 207 in http success status code RFC-4918"