The test suite local client now properly receives the events. Fixes #3214.

* We were instantiating the integration testing local client too soon in the process. Deferring it to a little latter made it all work.
* Added the ability to dump the master and minion testing configurations to files. Just prepend the `runtests` call with `DUMP_SALT_CONFIG=1` and you'll get the computed configuration files in `/tmp/salttest/{master,minion}`.
* We now also un-subscribe from the event's once done.
* Added `salt.utils.event.LocalClientEvent` just to differentiate from `salt.utils.event.MasterEvent` in the logs so we know who's who. It's just a subclass of the latter.