Add flush_my_map_info_list() and fix a bug in the Mac load_map_info_list().

(If you fclose(3) rather than pclose(3) a FILE* you got from popen(3),
future popen(3)s fail obscurely, at least on Mac OS.)

(cherry picked from commit 2bf76e143da933184d1392fb9bea3a3896c37e76)

Change-Id: I5578fe06753061b0dbc5ee951ebf31eb2bab0389