Fix a issue where using only mapfiels a auto.master isnt created

I ran into a issue where I created a mapfile but it didnt add it to the auto.master file so it wouldnt get sourced and setup. This fixes that.
Hrm.... I'm not sure about this. The !defined function is notoriously unreliable. Is it possible to  architect things differently so we know at this point if we've set it up in the master mountfile? Maybe simply requiring this resource here will either a) do the right thing or b) fail the catalog in such a way that the user can be reminded to add that somewhere?