Is it possible to install BIND 9.5.0-P1 over 8.4.6 without uninstalling
8.4.6 first?

The test machine has problem uninstalling 8.4.6, so I do not know if the
production machine will have the same problem. So it would be good to
skip uninstalling 8.4.6, but the current 9.5.0-P1 installer does not
allow this due to service name conflict.