Add a failure integration test case that requires mimic

Add test that requires mimic - inject server build failure, and test that the server fails to build.

This should pass on master, and should also still pass on #660 

The `time.sleep` is unfortunate, but since reads are consistency one....  :|  I did check that not injecting the error results in the test hanging until it fails.

I would also like to check that pending is 1 when we get the server creation response back, but unfortunately there is a bug associated with that (currently in the process of filing)

This takes advantage of [this particular](https://github.com/rackerlabs/mimic/blob/master/mimic/canned_responses/nova.py#L113) error injection feature in mimic.  The mechanism may change soon in a later version of mimic.
Do we have any data on how long it takes to get consistency in the test environment? (I am suddenly experiencing a flashback to that time when I didn't even get tcp over `lo` anymore due to an lxcl bug)