Disable key deleting for now, better fixes should be done later

Code for deletion of keys from keyauth_k looks suspicious.

Even if its correct, it ends up being too slow in livesync due to bad mergejoin (~2s per run). Livesync version could be speeded up by forcing a nestedjoin, but this might slow down massive sync version if it processes a lot more blocks at once, so might need to special case the code.

Given above, probably quickest solution at the moment is just to avoid deletion of keys: leave them in the keyauth_k, but simply not referenced in keyauth_a. This at least passes tests, so may be ok functionally. At first thought, seems unlikely there is any query that just wants to see if key is in keyauth_k only.

Currently benchmarking performance of this Q&D hack on s17.

The results: 17 keys weren't deleted on s17 that were deleted in previous state provider. Clearly key deletion isn't working properly already, so this fix (which speeds up things a lot) is being merged in. Later key deletion needs to be reviewed.