Change single write timer to per-send timers

Change single write timer to per-send timers

Previously, there was a single per-socket write timer that would get
restarted for every new write.  This turned out to be insufficient
because the other side could keep reseting the timer, and never reading
back the responses.

Change the single write timer to per-send timer which would in turn
reset the TCP connection on the first send timeout.

(cherry picked from commit a761aa59e3d988b53e2f42f45bce53f2bea863ec)