live statedb-injector will gobble ram if inserts get stuck

[matthewdarwin]

If the statedb-injector is running live and for some reason gets stuck injecting new k/v state, it will continue to pre-process arriving blocks. pre-processing is generally a good thing. But if the injector is stuck for a few hours, then the amount of RAM used might get excessive.

There should be some limit on RAM used or blocks processed or something.. And fall out of the READY state to alert operators of this issue