Fix server create for boot-from-volume

* server create required --image even when booting the server from a
  volume.  Change options to require either --image or --volume to
  specify the server boot disk.  Using --volume currently uses device
  'vda' for the block mapping and ignores any other block mappings
  given in --block-device-mapping.
* server create and server show are both affected by bug 1378842 where
  an excepion was thrown when no image ID was present in the returned
  server object, which is the case for a server booted from a volume.
* Fix the remaining assertEqual() order problems in test_server.py

Closes-Bug: 1378842
Closes-Bug: 1383338
Change-Id: I5daebf4e50a765d4920088dfead95b6295af6a4d
Unscoped federated user-specific commands

A federated user can authenticate with the v3unscopedsaml plugin and
list the domains and projects she is allowed to scope to.
This patch introduces the new commands 'federation domain list' and
'federation project list'.
Note that for these commands -and plugin- to be available, the lxml
library must be installed.

Change-Id: I2707b624befcfb0a01b40a094e12fd68a3ee7773
Co-Authored-By: Florent Flament <florent.flament-ext@cloudwatt.com>