Change test_post_alarm case in test_alarm_scenarios

It is not reasonable to assert that the new added object
will be the last one when call get_alarms, especially after
default sort direction is added.

Change-Id: Icd81aca5cd15e5ec34f081fe29fbad49dcccc45c
Change the error message of resource listing in mongodb

Seems that NotImplementedError can not be captured for some API level
test cases. So change the error message here that it can be captured.

Change-Id: I0ed87d3be8c908f7a23af6c24531e28d693c3240
Merge "Change test_post_alarm case in test_alarm_scenarios"
Merge "Change the error message of resource listing in mongodb"