Redis CPU load is so high when using Coverband::ResqueWorker with a lot of resque jobs and RedisHashStore

[FeLvi-zzz]

Is your feature request related to a problem? Please describe.

our production servers process a lot of resque jobs.

Coverband::ResqueWorker#perform reports when the job finished, so CPU utilization of our Redis store for collection coverage data goes too high.

Describe the solution you'd like

#572

Describe alternatives you've considered

none

Additional context

none