global: missing testsuites

* Adds a warning for when a testsuite file does not define a
  TEST_SUITE variable and thus not included in Travis test runs.

* Adds TEST_SUITE variable missing in tests for celery, oauth2server,
  oauthclient, pidstore, webhooks and utils modules.

* Fixes broken test cases.

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>