daemons: handle arguments correctly and uniformly

Of all daemons, only rapi did abort when given argument. None of our
daemons use any arguments, but they accepted them blindly. This is a
very bad experience for the user.

This patch adds checking and exiting in all daemons, in a uniform way.
One other option would have been to add a flag to GenericMain
(noargs=True).

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Olivier Tharan <olive@google.com>