quantum security group driver nova list shows same group

When using the quantum security group driver nova list shows the
same security group for all instances. This patch fixes this and
corrects the unit test that was hiding this bug. This also adds a unit test
to check that the default security group is added to the response when
not specified.

Fixes bug  1162077

Change-Id: I7a10f81af1bb6c93f634dc0de27841afe0f1f0ea
Merge remote-tracking branch 'm_src_repo/master' into build-temp