This patch update the way triggered checks of in-progress pairs are
handled, according to ICE spec, section 7.2.1.4. Previously the same
connection check was retransmitted with an updated timeout. This causes
problems when a controlling role switch occurs in this time frame.
This is the reason why a new connection check must be generated
reflecting the updated role. We introduce a new flag "recheck_on_timeout"
in the pair indicating that the pair must be rechecked at the next timer
expiration.

Differential Revision: https://phabricator.freedesktop.org/D875