Removes assertGreaterEqual for Python 2.6 backward compat

The unittest.TestCase class in python 2.6.6 does not have
an assertGreaterEqual method. Changes the code to use
assertTrue instead to guarantee backward compatibility with
Python 2.6.

Fixes Bug 1108238.

Change-Id: Ifaba250d9d9813de913be322d18541cd2dbdf28e
Merge "Removes assertGreaterEqual for Python 2.6 backward compat"