Use <once-button> for "find by perm" feature for Users, Roles

tailbone/templates/principal/find_by_perm.mako

@@ -116,10 +116,10 @@ ${h.end_form()}
     </div>
 
     <div class="buttons">
-      <b-button type="is-primary"
-                native-type="submit">
-        Find ${model_title_plural}
-      </b-button>
+      <once-button type="is-primary"
+                   native-type="submit"
+                   text="Find ${model_title_plural}">
+      </once-button>
     </div>
 
     ${h.end_form()}