Afr transaction performs lock, pre-op, op, post-op and unlock steps in that
    order. The child_up[] is overloaded with the information of where all
    the first two steps succeeded. This works perfectly fine for
    Transaction, but the locking/unlocking part of the code is re-used by
    data self-heal. In that each loop_frame does lock, rchecksum,
    read-from-source and write-to-sinks, unlock steps.
    
    Rchecksum fop assumes that the fop needs to happen on one source + all
    sinks and sets the call_count to that number. But if the lock step fails
    on any of the sinks it will mark the child_up of that child to 0, which
    will result in call_count mismatch and the frame will hang thinking that
    some more cbks need to come. When this happens loop_frame will never go
    to unlock step leading to hangs on that file.