Update to exit 1 on failure rollback

Signed-off-by: Riddhesh Sanghvi <[email protected]>

src/PHP.php

@@ -990,7 +990,7 @@ protected function rollback() {
 			$this->delete_site( $this->level, $this->site_data['site_url'], $this->site_data['site_fs_path'], $db_data );
 		}
 		\EE::success( 'Rollback complete. Exiting now.' );
-		exit;
+		exit( 1 );
 	}
 
 }