OSDs should disconnect from Monitor before their MOSDPGStat timeouts happen
Right now OSDs don't notice their monitor connection has dropped until after the (by default) 15 minute TCP connection timeout that the SimpleMessenger provides. This is doubly unfortunate because 15 minutes is also the timeout for them to not send MOSDPGStat messages to the monitor cluster.
Either the OSDs need to set a different TCP timeout; they need to independently notice they're not talking to the monitor, or we need to extend the MOSDPGStat timeouts. I'm leaning toward option 2 but haven't thought enough about the implications of each option.