Covering case where kwarg cannot be un-yaml'd

In the past the master has been taking the kwargs passed in and converting them to a string (kwy=value) and letting the minion de-yaml that arg string. In general this is okay, but it doesn't work well if you are calling from the python LocalClient interface-- since the kwarg you passed already had a type. With this change instead of converting the kwarg to a string it is converted to a dict with a flag to mark it as a kwarg dict, then it is unpacked on the minion side while still maintining type.

IMO we should parse out the YAML args on the master (never on the minion)-- that way all args on the minion side are already parsed and have a type. Bit confusing when you write code to pass data structures down and the transport messes it all up ;)