Call lcb_retryq_signal() when a new config has arrived

This will attempt to schedule all commands currently inside the retry
queue.

Change-Id: Id67b1debdbe4fc58736d31aa9c93848553d7c90e
Reviewed-on: http://review.couchbase.org/39255
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Brett Lawson <brett19@gmail.com>