Fix isc__nmsocket_stop(): make sockstop netievent as a high priority event (similarly to other transports)
Seemingly by omission, sockstop
netievent used by multi-layer sockets
was not a high priority event, like it should be (similarly to other
socket types).
In particular, that could make BIND stuck on reconfiguration after a DoH-listener is removed from the configuration.
This merge request fixes that too.
Closes #4071 (closed)
Edited by Artem Boldariev