Item compressor should not be scheduled if compression mode is not active

The ItemCompressorTask is scheduled to wake every 250ms, check if anything needs compressing and then sleep again.

This is fine if the compression mode is active, but if it is Passive or Off then the task is being woken and run (briefly) every 250ms per Bucket. This is essentially pointless work.

We should modify the scheduling to only schedule if Compression is set to Active, otherwise to not schedule it at all (and wake if the mode changes to Active).