Add a use_master_when_local option to allow remote execution while using...

... a local file_client

This PR allows for remote execution while using a salt master for remote execution. This option will obviously have some side effects. For instance, the cp module will be slightly confusing, as it will trigger a cp to/from the minion to/from the master, which in this case would also be the minion.

However, this option makes it possible to do salt runs from the master successfully.
This line is pretty funny, btw. With the line above, it's functionally 'and True'.