Fix incorrect usage of assertTrue()

The usage of assertTrue() is incorrect, more explicit assert
from the unit test suite(like assertIsNotNone or assertIn)
should be used instead.

Fixes: bug #1217028
Change-Id: I30a80bc9e122d28c22b698e0cb97068c1040bfc3
Signed-off-by: Rosario Di Somma <rosario.disomma@dreamhost.com>
Merge "Fix incorrect usage of assertTrue()"