identity v3 allow project list filtering by domain

The underlying keystoneclient interface allows filtering by domain,
so support it in the cli interface because it makes project list
much nicer to use in a multi-domain deployment.

Change-Id: If3f5cf1205c1e9cf314f8286a3ae81bda4456b8f
Closes-Bug: #1289513
Merge branch 'review/steven_hardy/79040' into dt-test
Merge branch 'identity-ec2-tests' into dt-test