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) {

model/utils.go

@@ -18,6 +18,7 @@ import (
 	"regexp"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 	"unicode"
 
@@ -72,10 +73,13 @@ func (sa StringArray) Equals(input StringArray) bool {
 	return true
 }
 
-var translateFunc goi18n.TranslateFunc = nil
+var translateFunc goi18n.TranslateFunc
+var translateFuncOnce sync.Once
 
 func AppErrorInit(t goi18n.TranslateFunc) {
-	translateFunc = t
+	translateFuncOnce.Do(func() {
+		translateFunc = t
+	})
 }
 
 type AppError struct {

scripts/test.sh

@@ -16,7 +16,7 @@ echo "Packages to test: $PACKAGES"
 find . -name 'cprofile*.out' -exec sh -c 'rm "{}"' \;
 find . -type d -name data -not -path './vendor/*' -not -path './data' | xargs rm -rf
 
-$GO test $GOFLAGS -run=$TESTS $TESTFLAGS -v -timeout=2000s -covermode=count -coverpkg=$PACKAGES_COMMA -exec $DIR/test-xprog.sh $PACKAGES 2>&1 > >( tee output )
+$GO test $GOFLAGS -run=$TESTS $TESTFLAGS -v -timeout=20m -covermode=count -coverpkg=$PACKAGES_COMMA -exec $DIR/test-xprog.sh $PACKAGES 2>&1 > >( tee output )
 EXIT_STATUS=$?
 
 cat output | $GOBIN/go-junit-report > report.xml