With oslo-incubator going away, we need to pull those classes into
the Manila code base, along with their unit tests. This presents a
good opportunity to do some long-needed housecleaning. This commit
does the following:
1. Moves the scheduler classes from openstack.common to manila.
2. Adds the unit tests from olso-incubator into Manila.
3. Removes duplication among the combined scheduler modules.
4. Moves scheduler drivers into a sub-module.
5. Normalizes class and module naming throughout the scheduler.
6. Splits some unit test files so they match the names of the
modules that they test.
7. Converts usage of mox & oslotest to mock & unittest.
8. Adds a few unit tests to boost coverage levels.
Implements: blueprint reorganize-manila-scheduler
Change-Id: I7aa237e17787e89a95bb198093ea9bc9498279cd
af2e103514