Use a more sensible network topology for some router tests

This is achieved by creating subnets on separate logical
networks. A negative tests is also added to verify that
interface attachment fails when done with overlapping
subnets.

Closes-bug: #1316742

Change-Id: Idb1965e32d30acd962e1a3fa755b6c8b25c1bc31
Convert get_console_output length=None to -1 for Nova V3 API calls

Nova commit 8e5577f52f660960738f1fc0384dff77fa30fc8a makes the nova v3
get_console_output extension handle unlimited length with -1.

In the nova v2 API the length parameter is optional but the nova v3 API
uses jsonschema validation so it expects a value to check against.

Closes-Bug: #1328582

Change-Id: Ib1ae85e644e08c24aaf0ba2baaa8812286ef0ebd
Cleanup for local variable in test_attach_volume

This patch cleanup the test_attach_volume for unnecessary and
unused local variable.

During https://review.openstack.org/#/c/87191/7/, it came out
that we should clean up this file for unnecessary local variable.
So for logical breakdown of changes, this patch do the cleanup
part separately.

Change-Id: I4afc88a09f43f8b068b16368cbddb4bff21059c6
Merge "Cleanup for local variable in test_attach_volume"
Merge "Convert get_console_output length=None to -1 for Nova V3 API calls"
Merge "Use a more sensible network topology for some router tests"