Fix inheritance in the LVM tests to prevent multiple runs of some tests
Fix inheritance in the LVM tests to prevent multiple runs of some tests

If some test case class is inherited from a class that has its own tests, such
tests get run multiple times which is not necessary and only makes running test
suite longer.

vpodzime/libblockdev,atodorov/libblockdev,rhinstaller/libblockdev,vpodzime/libblockdev,atodorov/libblockdev,rhinstaller/libblockdev,atodorov/libblockdev,vpodzime/libblockdev,rhinstaller/libblockdev