Close the IO from the read loop thread

IO#close and IO#read across threads don't get along so well:

After T1 enters #read and releases the GVL, T2 can call #close on the
IO, thereby both closing the fd and freeing the buffer while T1 is using
them.

actioncable/lib/action_cable/connection/stream.rb

@@ -106,7 +106,6 @@ def hijack_rack_socket
         def clean_rack_hijack
           return unless @rack_hijack_io
           @event_loop.detach(@rack_hijack_io, self)
-          @rack_hijack_io.close
           @rack_hijack_io = nil
         end
     end

actioncable/lib/action_cable/connection/stream_event_loop.rb

@@ -36,6 +36,7 @@ def detach(io, stream)
         @todo << lambda do
           @nio.deregister io
           @map.delete io
+          io.close
         end
         wakeup
       end