Today, if a customer wants to change the router_checker ping rate, they need to change the module parameters on every client/server and reload LNet.  That is painful on a large production cluster.

This ticket proposes we have routers put a timeout value in the ping replies instructing the clients/servers when next to ping.  Then, if this can be controlled via lnetctl dynamically, customers can change the ping rate by just issuing an lnetctl command on the handful of LNet routers and do not have to change clients/servers at all.

This will also be useful later on with LNet Health as congestion detection in a router can trigger a larger timeout value on all router ping replies.