Close instead of sending on channel

I think that closing the channel makes it clearer that this channels purpose has been fulfilled and it no longer needs to be considered. All the places that use the channel are recieving all values from the channel so they will continue to function in the same way

pkg/server/backuprestoreserver.go

@@ -536,7 +536,7 @@ func handleSsrStopRequest(ctx context.Context, handler *HTTPHandler, ssr *snapsh
 		ssr.SsrStateMutex.Lock()
 		if ssr.SsrState == brtypes.SnapshotterActive {
 			ssr.SsrStateMutex.Unlock()
-			ssrStopCh <- emptyStruct
+			close(ssrStopCh)
 		} else {
 			ssr.SsrState = brtypes.SnapshotterInactive
 			ssr.SsrStateMutex.Unlock()