WPS: Abort ongoing PBC protocol run if session overlap is detected

WPS: Abort ongoing PBC protocol run if session overlap is detected

If PBC session overlap is detected during an ongoing PBC protocol run,
reject the run (if M8, i.e., credentials, have not yet been sent). This
provides a bit longer monitoring time at the Registrar for PBC mode to
catch some cases where two Enrollees in PBC mode try to enroll
credentials at about the same time.