Now that 2.6 is essentially finished and 2.7 going to be branched
soon-ish, I thought it would be a good moment to replace some single
quotes in test/*.py. Merge pains should be limited.

In one place in test/ganeti.locking_unittest.py, spaces are added for
assignments.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>