In the stop method of ConnectionManager to cancel the ackTimeoutMonitor

cc JoshRosen sarutak

Author: GuoQiang Li <witgo@qq.com>

Closes #1989 from witgo/cancel_ackTimeoutMonitor and squashes the following commits:

4a700fa [GuoQiang Li] In the stop method of ConnectionManager to cancel the ackTimeoutMonitor

(cherry picked from commit bc95fe08dff62a0abea314ab4ab9275c8f119598)
Signed-off-by: Josh Rosen <joshrosen@apache.org>