Change 6449c59 brought back abort on listener failure, but this causes crashes when listeners hit expected errors like gate_closed.
Detect shutdown usig the gossiper _abort_source
and in this case just log a warning about the errors but do not abort.
Fixesscylladb/scylladb#15031Closes#15100
* github.com:scylladb/scylladb:
gossiper: apply_new_states: tolerate listener errors during shutdown
gossiper: do_on_change_notifications: check abort source
gossiper: lock_endpoint_update_semaphore: get_units with _abort_source
gossiper: lock_endpoint: get_units with _abort_source
gossiper: is_enabled: consider also _abort_source