Remove unnecessary check to see if trustee exists

Previously we check if the returned trustee value is None, this
is already done at the backend level.

Change-Id: I801bed09300782e289ee505612df09f7270fcb4e
Clean up database fixtures

 - Issues setting up the DB will now break early instead of causing
   issues later in tests.
 - Databases are now removed at the end of the test run.

Change-Id: I1dc5feafa9ae88fc0f2a4dd9459e7e34e2c4ce73
Add tests for oauth consumer normalize fields

There were no tests that verified that fields in oauth consumers
were normalized as expected. The tests show that the fields aren't
being normalized as expected on update.

Change-Id: I3bc95766b61d8dc8c85b32f628b275721255e95d
Related-Bug: #1276857
Provide clearer error when deleting enabled domain

Currently the message is confusing, because it reads like an instruction
to delete an enabled domain, rather than an instruction that you can
only delete disabled domains.  Hopefully this wording is a little clearer
for users.

Change-Id: I5189cd1bbae0e485d03660be19f20879110a3b3e
Closes-Bug: #1279823
Merge "Provide clearer error when deleting enabled domain"
Merge "Remove unnecessary check to see if trustee exists"
Merge "Add tests for oauth consumer normalize fields"
Merge "Clean up database fixtures"