Test threaded: more margin.
Test threaded: more margin.

This is anoying, but I see no other way to test if two operations are
serial or parallel than to use delays.

	* src/uobjects/threaded.uob/threaded.cc: 300->500ms sleep.

urbiforge/urbi,aldebaran/urbi,aldebaran/urbi,urbiforge/urbi,urbiforge/urbi,aldebaran/urbi,aldebaran/urbi,aldebaran/urbi,aldebaran/urbi,aldebaran/urbi,aldebaran/urbi,urbiforge/urbi,urbiforge/urbi,urbiforge/urbi,urbiforge/urbi,urbiforge/urbi,urbiforge/urbi