py/runtime: Make mp_load_method_maybe() stop after dispatching to ->attr.
py/runtime: Make mp_load_method_maybe() stop after dispatching to ->attr.

This is the original behavior of this routine, which was changed to
facilitate working with native types which have both ->attr and
->locals_dict. But doing it this way leads to weird interaction
with instance-based lookup in objtype.c (mp_obj_class_lookup). So,
get back to invariant that lookup is completely handled by either
->attr or mp_load_method_maybe(). Types which have ->attr, but also
want to lookup in ->locals_dict, should explicitly call
mp_load_method_maybe_from_locals_dict() in their ->attr().

Change-Id: I15dbc83b0ba2dfb971d76a43ebc2b912182346f4
Signed-off-by: Paul Sokolovsky <9dc5061f178bb11813e14f1ed02ba27eaf21fa5d@users.sourceforge.net>

pfalcon/micropython,pfalcon/micropython,pfalcon/micropython,pfalcon/micropython,pfalcon/micropython