MINOR: add icon to ajax button in AssetAdmin

code/controllers/AssetAdmin.php

@@ -178,7 +178,7 @@ public function getEditForm($id = null, $fields = null) {
 			$syncButton = new LiteralField(
 				'SyncButton',
 				sprintf(
-					'<a class="ss-ui-button ss-ui-action cms-link-ajax" title="%s" href="%s">%s</a>',
+					'<a class="ss-ui-button ss-ui-action ui-button-text-icon-primary ss-ui-button-ajax" title="%s" href="%s">%s</a>',
 					_t('AssetAdmin.FILESYSTEMSYNCTITLE', 'Update the CMS database entries of files on the filesystem. Useful when new files have been uploaded outside of the CMS, e.g. through FTP.'),
 					$this->Link('doSync'),
 					_t('FILESYSTEMSYNC','Sync files')
@@ -446,6 +446,7 @@ public function SiteTreeAsUL() {
 	public function doSync() {
 		$message = Filesystem::sync();
 		$this->response->addHeader('X-Status', $message);
+
 		return;
 	}