This patch add two supplementary cases, not covered by the ICE spec,
sect 7.2.1.5 "Updating the Nominated Flag" when a controlled agent
receives a STUN request with the USE-CANDIDATE flag, for a pair that is
in the waiting state. We consider that this case is similar to the
in-progress state, and should be handled in the same way. We also accept
when the pair is in frozen state. This latter case happens in the
new-dribble test, when an agent replays incoming early connchecks.

Differential Revision: https://phabricator.freedesktop.org/D880