It is bitcoin gui or the daemon running you cannot have both going at the same time they conflict as you have seen already.
But only the daemon (bitcoind) was running.
After my OP I tried to open the GUI version, and it displayed the lock error as I would expect.
Just to make sure, I just did a ps -u, saw only "bitcoind - daemon", issued the -rpcallowip command, and got the same error.