Reduce utils.Cfg references (#7650)

* app.UpdateConfig method

* test fix

* another test fix

* the config override option as-was is just error prone, remove it for now

* derp

app/elasticsearch.go

@@ -7,13 +7,12 @@ import (
 	"net/http"
 
 	"github.com/mattermost/mattermost-server/model"
-	"github.com/mattermost/mattermost-server/utils"
 )
 
 func (a *App) TestElasticsearch(cfg *model.Config) *model.AppError {
 	if *cfg.ElasticsearchSettings.Password == model.FAKE_SETTING {
-		if *cfg.ElasticsearchSettings.ConnectionUrl == *utils.Cfg.ElasticsearchSettings.ConnectionUrl && *cfg.ElasticsearchSettings.Username == *utils.Cfg.ElasticsearchSettings.Username {
-			*cfg.ElasticsearchSettings.Password = *utils.Cfg.ElasticsearchSettings.Password
+		if *cfg.ElasticsearchSettings.ConnectionUrl == *a.Config().ElasticsearchSettings.ConnectionUrl && *cfg.ElasticsearchSettings.Username == *a.Config().ElasticsearchSettings.Username {
+			*cfg.ElasticsearchSettings.Password = *a.Config().ElasticsearchSettings.Password
 		} else {
 			return model.NewAppError("TestElasticsearch", "ent.elasticsearch.test_config.reenter_password", nil, "", http.StatusBadRequest)
 		}