Move decision_maker() call into setUpClass

Previously the class level call of decision_maker() to detect certain
configuration details for the boto tests was mad in the class
definition. This has issues with unit testing because it requires a
functional config at import time for the file. This commit avoids this
restriction by moving this call into setUpClass for BotoTestCase which
won't try to execute decision_maker() at import.

Change-Id: I8abf4ae109576499fed6b31ae644c1bac58e3350
Merge "Move decision_maker() call into setUpClass"