Save observations and configuration statuses together

[eheinrich]

There was an error while serializing the response for a GET request to /api/schedule/. The error was a KeyError that was raised in the as_dict method of an Observation here, which suggests that a configuration status did not exist for one of the observation's configurations at the time of the method call.

The time of the error corresponds with the creation time of the observation in question- The observation was created at UT 9/8 05:34:00 and the timestamp in the error email is UT 9/8 05:34:05.

I've wrapped observation creation in a transaction so that an Observation will not be included in a queryset until both it and its config statuses have been saved. In the ScheduleSerializer save method, I included saving the request group in the transaction as well since I figure that if there is an error creating the observation, we probably don't want to keep the requestgroup around... Let me know what you think about that, especially given the work that you've been doing on your deadlock fixes branch.

[coveralls]

Coverage increased (+0.001%) to 96.039% when pulling 8bd027d on fix/configstatus-race into 2401f3b on master.

[jnation3406]

yeah these look like good changes, they shouldn't interfere with my branch