ui: datastore/Summary: change destroy listener

by using beforedestroy instead of destroy (like we do everywhere else)
to avoid race condition when the controller has
already removed some handlers on destruction

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>

www/datastore/Summary.js

@@ -86,7 +86,7 @@ Ext.define('PBS.DataStoreInfo', {
 
     listeners: {
 	activate: 'startStore',
-	destroy: 'stopStore',
+	beforedestroy: 'stopStore',
 	deactivate: 'stopStore',
     },