MM-14082 Don't print warnings when saving duplicate metadata (#10376)

* MM-14082 Don't print warnings when saving duplicate metadata

* Fix order of arguments passed to assert.Equal

store/sqlstore/link_metadata_store.go

@@ -45,7 +45,7 @@ func (s SqlLinkMetadataStore) Save(metadata *model.LinkMetadata) store.StoreChan
 		metadata.PreSave()
 
 		err := s.GetMaster().Insert(metadata)
-		if err != nil {
+		if err != nil && !IsUniqueConstraintError(err, []string{"PRIMARY", "linkmetadata_pkey"}) {
 			result.Err = model.NewAppError("SqlLinkMetadataStore.Save", "store.sql_link_metadata.save.app_error", nil, "url="+metadata.URL+", "+err.Error(), http.StatusInternalServerError)
 			return
 		}