Stop using all dirauth-only options in shared_random_client.c

This is not as clean a patch as I would like: see the comment on
ASSUME_AUTHORITY_SCHEDULING. This issue here is that the unit tests
sometimes assume that we are going to be looking at the dirauth
options and behaving like a dirauth, but without setting the options
to turn is into one.

This isn't an issue for actually running Tor, as far as I can tell
with chutney.