Eliminate proto_tree_add_text from some plugin dissector files.

Change-Id: Ib2d900833a8763307be6b1cfc8df20d7019d2706
Reviewed-on: https://code.wireshark.org/review/5313
Petri-Dish: Michael Mann <mmann78@netscape.net>
Reviewed-by: Michael Mann <mmann78@netscape.net>