- Do nothing in case the session is closed, to prevent we fire up the
timer again
- Print log info when no progress has been made if the time expires, it
is very useful to debug a idle session
- Grab a reference when the keep alive timer is running
Message-Id: <9f2cc3164696905a6a39c0d072a980765d598dfd.1458782956.git.asias@scylladb.com>