run-cloud-providers option added

@s0undt3ch - I have been writing some initial tests for testing basic Salt-Cloud functionality. The idea is to test basic "create an instance" and "delete the instance" functionality with each provider. @techhat wanted the tests to be off by default, so I have made a "--run-cloud-providers" flag with a decorator, similar to "--run-destructive". I don't think we want these on all of the time on Jenkins, but available to run as needed to catch API changes and such.

Can you take a look at the changes here as well as my forth-coming PR on salt? Feedback is much appreciated! :)