Fixed values passed in to get_combo_xml and get_dtype_combo_xml calls.

Fixed values passed in to get_combo_xml and get_dtype_combo_xml calls methods to rebuild Type and Data Type DhtmlxCombos on schema editor screen.

https://bugzilla.redhat.com/show_bug.cgi?id=1087930
https://bugzilla.redhat.com/show_bug.cgi?id=1109984

@dclarizio please review/test. This was blowing up when trying to delete a schema field after adding a new one.