[MM-19004] Change assertion in client4/system_test.go to be less flaky (#12586)

* avoid swallowing errors from websocket_client.SendMessage

* Revert "avoid swallowing errors from websocket_client.SendMessage"

This reverts commit 5f223e0996f59f31792607c8a4fbf63bf42040ee.

* test against app.TotalWebsocketConnections instead of hardcoding assertion

api4/system_test.go

@@ -383,7 +383,7 @@ func TestGetAnalyticsOld(t *testing.T) {
 	rows2, resp2 = th.SystemAdminClient.GetAnalyticsOld("standard", "")
 	CheckNoError(t, resp2)
 	assert.Equal(t, "total_websocket_connections", rows2[5].Name)
-	assert.Equal(t, float64(1), rows2[5].Value)
+	assert.Equal(t, float64(th.App.TotalWebsocketConnections()), rows2[5].Value)
 
 	WebSocketClient.Close()