Ensure that errors are returned as JSON and not plain text description.

Change that was made to apigee/usergrid but did not make it into usergrid/usergrid in time for the Apache import.
Fixing tests broken by error handling changes.

Change that was made to apigee/usergrid but did not make it into usergrid/usergrid in time for the Apache import.
See also: https://github.com/apigee/usergrid-stack/pull/257
Reduce repetitive logging in three specific locations that are noisy and repetitive during testing. The first exception of any given type is logged at ERROR level with a stack trace and subsequent instances of the same exception are logged without a stack trace (unless debug is turned on).

Change that was made to apigee/usergrid but did not make it into usergrid/usergrid in time for the Apache import.
See also: https://github.com/apigee/usergrid-stack/pull/257