Remove ilios.gm.mm.sortFilteredResults

ilios.gm.mm.sortFilteredResults was only ever called by itself.  Which
is a lonely kind of recursion.
Redraw the selection tree on every refresh

Usually ilios.gm.mm.redrawTreeAndUpdateCSS gets called when the list of
users is filtered, however when that list is empty (all users already
selected) it was not getting called at all.
Test for duplicated in learner group picker

This test ensures that the learner picker is refreshed on each load and
doesn’t hold onto its state when it is opened twice.