MINOR: ring: support inactivity timeout in show ring CLI handler

MINOR: ring: support inactivity timeout in show ring CLI handler

This patch implements uninterruptible mode of execution when monitoring
a ring via the CLI. The handler continues to run despite the detection
of the CLI input closure.

The command is still stopped if a send error occurs while reporting new
events. Also, the socket timeout is reused as an inactivity timeout,
refreshed each time new events are detected. The command is stopped if
there is nothing to report during this delay.