Clean up comparison assertions

Clean up comparison assertions

Using assertTrue and the comparison operators to test
if an element is greater, equal, or less is too python2.4.
Our unit testing framework 'testtools' supports
- assertEqual
- and testtools Matcher classes
which were created for these types of tests.

Re-implemented assertGreater and assertGreaterEqual
with compatibility for python < 2.7.

Change-Id: I6f3e3279630393e594c75d30cb4b895c2e2c22ca