BUG/MINOR: Wrong peer task expiration handling during synchronization processing.

BUG/MINOR: Wrong peer task expiration handling during synchronization processing.

When a peer task has sent a synchronization request to remote peers
its next expiration date was updated based on a resynchronization timeout
value which itself may have already expired leading the underlying
poller to wait for 0ms during a fraction of second (consuming high CPU
resources).

With this patch we update such peer task expiration dates only if
the resynchronization timeout is not already expired.

Thanks to Patrick Hemmer who reported an issue with nice traces
which helped in finding this one.

This patch may be backported to 1.7 and 1.6.