Move DRBD tests into tests/unit

We've reorganized since the original driver code was
written, move this into the right directory.

Change-Id: I88b970e2726191c8cd795c5ddbb64784a465db65

diff --git a/cinder/tests/test_drbdmanagedrv.py b/cinder/tests/unit/test_drbdmanagedrv.py
similarity index 100%
rename from cinder/tests/test_drbdmanagedrv.py
rename to cinder/tests/unit/test_drbdmanagedrv.py