This PR fixes an issue where the remote worker was stopped twice and not
properly handled. This adds a synchronised running check to the start
and stop methods preventing closing of a channel more than once.
There are a bunch of changes required to make this work:
- in miner: allow unregistering agents, fix RemoteAgent.Stop
- in eth/filters: make FilterSystem.Stop not crash
- in rpc/comms: move listen loop to platform-independent code
Fixes#1930. I ran the shell loop there for a few minutes and didn't see
any changes in the memory profile.
Work is now handled and carried over multiple sessions. Previously one
session only was assumed, potentially resulting in invalid (outdated)
work
* Larger work / result queue
* Full validation option
