1592a84b80
Passing the gate_closed_exception to the task promise in start()
ends up with abandoned exception since no-one is waiting
for it.
Instead, enter the gate when the task is made
so it will fail make_task if the gate is already closed.
Fixes scylladb/scylladb#15211
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
(cherry picked from commit f9a7635390)