As 284, part 1 - find a created server on Nova (ready for review)

This change is bigger than I thought, so I am trying to break it up into bits.  This part just provides the functionality to check Nova for an exact server that matches a given server config, created around a certain time.

Question for the next part - should we wait at all after getting a 500 or 401 response back from Nova from creating a server, before checking Nova to see if a server was created? 
> that nova may return wrong data

I wonder how much otter can actually work if Nova returns wrong data. However, we've noticed that change operations like POST/DELETE are unreliable. Most of the GETs have been pretty reliable. So, I think this may not be concern here. 

> the amount of randomness on our cloud servers

Which randomness are you worried about? I clearly do not have enough knowledge on randomness so I am sure you might have some valid point here.