Bug 238031: cluster mirrors not handling all recovery/write conflicts
    
    Problem is that the kernel (main mirror code) does not do any marks/clears when
    writing to a region before its recovery.  So, it is not possible for the server
    to detect a conflict.  Basically, we must turn back on the
    'is_remote_recovering' function and disallow any writes to regions that are OR
    WILL BE recovering.
    
    It's really going to cause some pain during writes while mirrors are re-syncing.
    The better fix for the future is to have the writes always mark/clear the
    regions - then we can again remove the 'is_remote_recovering' function.