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

api/admin.go

@@ -235,12 +235,12 @@ func getAnalytics(c *Context, w http.ResponseWriter, r *http.Request) {
 }
 
 func uploadBrandImage(c *Context, w http.ResponseWriter, r *http.Request) {
-	if r.ContentLength > *utils.Cfg.FileSettings.MaxFileSize {
+	if r.ContentLength > *c.App.Config().FileSettings.MaxFileSize {
 		c.Err = model.NewAppError("uploadBrandImage", "api.admin.upload_brand_image.too_large.app_error", nil, "", http.StatusRequestEntityTooLarge)
 		return
 	}
 
-	if err := r.ParseMultipartForm(*utils.Cfg.FileSettings.MaxFileSize); err != nil {
+	if err := r.ParseMultipartForm(*c.App.Config().FileSettings.MaxFileSize); err != nil {
 		c.Err = model.NewAppError("uploadBrandImage", "api.admin.upload_brand_image.parse.app_error", nil, "", http.StatusBadRequest)
 		return
 	}
@@ -358,7 +358,7 @@ func samlMetadata(c *Context, w http.ResponseWriter, r *http.Request) {
 }
 
 func addCertificate(c *Context, w http.ResponseWriter, r *http.Request) {
-	err := r.ParseMultipartForm(*utils.Cfg.FileSettings.MaxFileSize)
+	err := r.ParseMultipartForm(*c.App.Config().FileSettings.MaxFileSize)
 	if err != nil {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
 		return