Fix resource mapping for Docker

resource_mapping() always returns all existing resource names and
their classes. available_resource_mapping() takes the dependencies
into account and only returns the ones whose dependencies have been
met.

Co-Authored-By: Richard Lee <rblee88@gmail.com>
Partial-Bug: #1271226
Change-Id: I3d785d92f1d30a3caf4cb0f7721c66c9dda294c3
Change Docker resource mapping name

Removing the OS:: prefix since this is not an OpenStack-provided
resource.  Also remove hardcoded resource mapping name in test.

Co-Authored-By: Anderson Mesquita <andersonvom@gmail.com>
Partial-Bug: #1271226
Change-Id: I5691a08df3700f896ca1fe6efec4487d44617d6d
Merge "Fix resource mapping for Docker"
Merge "Change Docker resource mapping name"