ui: backup view: add scrolling overflow handler for the toolbar

As we got reports that some buttons get cut-off on resolutions close
to our minimal 720p one, especially if the "guest not in backup" jobs
hint is shown.

Link: https://forum.proxmox.com/threads/120714/
Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
 [ T: resolve merge conflict and reword commit message ]
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

www/manager6/dc/Backup.js

@@ -740,7 +740,11 @@ Ext.define('PVE.dc.BackupView', {
 	    viewConfig: {
 		trackOver: false,
 	    },
-	    tbar: [
+	    dockedItems: [{
+		xtype: 'toolbar',
+		overflowHandler: 'scroller',
+		dock: 'top',
+		items: [
 		    {
 			text: gettext('Add'),
 			handler: function() {
@@ -775,6 +779,7 @@ Ext.define('PVE.dc.BackupView', {
 			},
 		    },
 		],
+	    }],
 	    columns: [
 		{
 		    header: gettext('Enabled'),