Utilizes assertIsNone and assertIsNotNone - tests/virt

Using assertTrue and the 'is None' operator to test if an element is None
is too python2.4. Our unit testing framework 'testtools' supports
assertIsNone and assertIsNotNone, included from python 2.7,
which were created for these types of tests.

Change-Id: Iee1379b941f93388900e89388676000b845fc8fc
Merge "Utilizes assertIsNone and assertIsNotNone - tests/virt"