Properly end negotiations. #5125
Properly end negotiations. #5125

As noted in #5174, we can't just send END_NEGOTIATE to the schedd
whenever we want to stop negotiation - if we do, it'll leave
scary-looking log messages schedd-side.

Fix implementation of the negotiation protocol to make sure
END_NEGOTIATE is used only when proper.

htcondor/htcondor,htcondor/htcondor,htcondor/htcondor,htcondor/htcondor,htcondor/htcondor,htcondor/htcondor,htcondor/htcondor,htcondor/htcondor