Add slave/master end-to-end test

Add slave/master end-to-end test

Added a MountPointEndToEndTest that tests master and slave
mount point operations end-to-end with as little mocking as
possible. Hooks were added in NetconfTopologyContext and MasterSalFacade
for the MountPointEndToEndTest to get a hold of the MasterSalFacade
to invoke it manually to simulate backend device connectivity and to
inject the backend DOMDataBroker.

Change-Id: I5cc59987570ba4e99980af4e2f4c5adf47b6a81e
Signed-off-by: Tom Pantelis <tompantelis@gmail.com>
(cherry picked from commit 948fe9d5f58b0382a322003d74fa6496f45caab8)