Refactor plugin.py and midonet_lib.py to improve unit testing of
the MidoNet plugin. Make all the tests pass in the plugin except
those that test features that are not currently supported by the
plugin, which are IPv6 and multiple subnets per network.
Consolidate the mocking code in mock_lib.py to be shared by
plugin.py and midonet_lib.py.
Change-Id: Idcdfc3d90d5ec9e0be29bb6833d336af596fe363
Fixes: bug #1133215
Signed-off-by: Ryu Ishimoto <ryu@midokura.com>
Signed-off-by: Tomoe Sugihara <tomoe@midokura.com>