choose circuit ID types.  This is important because our view of "the
nickname of the router on the other side of this connection" is
skewed, and depends on whether we think the other rotuer is
verified--and there's no way to know whether another router thinks you
are verified.

For backward compatibility, we notice when the other router chooses
the same circuit ID type as us (because it's running an old version),
and switch our type to be polite.


svn:r2797