Check rescue_server action attributes of Nova APIs

This patch adds the JSON schema for Nova V2 & V3 rescue server
action APIs response and validate the response with added JSON schema
to block the backward incompatibility change in the future.

For V3 API, "admin_password" in response body is depend on config
variable "enable_instance_password". So schema and request
is adjusted accordingly.
NOTE - V2 rescue API's response does not on above config variable.

The response body of rescue server V2 APIs is below:
{
    "adminPass": "%(password)s"
}

The response body of rescue server V3 APIs is below:
If CONF.enable_instance_password is true-
{
    "admin_password": "%(password)s"
}
Else
    {}

Partially implements blueprint nova-api-attribute-test

Change-Id: I85f18eaa58bfef1871100816f97487f9fa9bc0ee
Avoid errors in log when neutron tests are skipped

The BaseNetworkTest class setUpClass() method will initialize
various class attributes which the tearDownClass() method
expects to exist. Unfortunately when Neutron is not
available, the entire of the setUpClass() method is skipped,
but tearDownClass() still runs. This causes the logs to get
polluted with errors about missing attributes during
tearDownClass(). eg

ERROR tempest.test [-] tearDownClass failed: type object
 'DHCPAgentSchedulersTestJSON' has no attribute 'ipsecpolicies'
TRACE tempest.test     for ipsecpolicy in cls.ipsecpolicies:

Make the tearDownClass() code be conditional on neutron
being enabled too.

Change-Id: I042ca5c47e5c1e8d1042754fd7f36036a40b2f03
Merge "Avoid errors in log when neutron tests are skipped"
Merge "Check rescue_server action attributes of Nova APIs"