MM-30988 - Fix racy test ServerSystemdNotification (#16431)

* MM-30988 - Fix racy test ServerSystemdNotification

The translateFunc is a global variable which was unguarded.
So we convert that into an atomic variable to prevent against races.

https://mattermost.atlassian.net/browse/MM-30988

```release-note
NONE
```

* fix tests

* move call upwards

* use race

* after translations init

* guard with a sync.Once

* missed import

* revert race

* update timeout

app/server.go

@@ -269,6 +269,7 @@ func NewServer(options ...Option) (*Server, error) {
 	if err := utils.TranslationsPreInit(); err != nil {
 		return nil, errors.Wrapf(err, "unable to load Mattermost translation files")
 	}
+	model.AppErrorInit(utils.T)
 
 	searchEngine := searchengine.NewBroker(s.Config(), s.Jobs)
 	bleveEngine := bleveengine.NewBleveEngine(s.Config(), s.Jobs)
@@ -450,8 +451,6 @@ func NewServer(options ...Option) (*Server, error) {
 		mlog.Error("Problem with file storage settings", mlog.Err(appErr))
 	}
 
-	model.AppErrorInit(utils.T)
-
 	s.timezones = timezones.New()
 	// Start email batching because it's not like the other jobs
 	s.AddConfigListener(func(_, _ *model.Config) {