Port server actions unittests to V3 API Part 2

Ports the server actions unittests to test the V3 API.
This mostly involved CamelCase to camel_case changes
and adpating the URLs to point to the V3 API instead of
the V2 API.

It also includes
- Fixing a bug in the admin_password extension picked up by
  the tests where bad request data is not always handled properly
- Generate image ref urls that point to glance api rather than
  the nova api. This fits in with the decision to not port the images
  extension to the V3 API which is implemented here:
  https://review.openstack.org/#/c/40565/
- Moves admin password related tests to the admin password unittests
  test file as this functionality has been moved out from core.

Partially implements blueprint v3-api-unittests

Change-Id: I58b4c0103c824898183fca890c74c3c1cbe19633
Call baselineCPU for full feature list

Since the libvirt API getCapabilities doesn't return a full list of CPU features we need
to call the libvirt API baselineCPU with the new flag VIR_CONNECT_BASELINE_CPU_EXPAND_FEATURES
to get all features.

Since the flag is new this code checks for its existence before calling baselineCPU.

Also, due to some rather stringent input checking on libvirt's part, just calling
baselineCPU with the output from getCapabilities doesn't work, you have to extract
just the <cpu> stanza from the XML returned by getCapabilities.

Add unit test to make sure that the current verion of libvirt works (although
it will hide some features) and the new version of libvirt will correctly
return all features.

Fixes bug 1217630

Change-Id: I266bacb7e0c79d9c5b13ff163f01d14cad9ab57b
Merge "Port server actions unittests to V3 API Part 2"
Merge "Call baselineCPU for full feature list"