application: fallback on sys.argv when no arguments are provided

the previous behavior was error prone. specify [] to have no arguments given. (not needed in the normal case)

Change-Id: I9b532eef85d676b1390610f87484524ae0e3bd59
Reviewed-on: http://gerrit.aldebaran.lan/45753
Reviewed-by: cgestes <gestes@aldebaran-robotics.com>
Tested-by: cgestes <gestes@aldebaran-robotics.com>