Fix CliRunnerCallbacks.on_file_diff in callbacks.py

When running ansible -C, I get a traceback that ends with
    AttributeError: Values instance has no attribute 'diff'
This fixes on_file_diff to behave similar to
PlaybookRunnerCallbacks.on_file_diff().

lib/ansible/callbacks.py

@@ -285,7 +285,6 @@ class CliRunnerCallbacks(DefaultRunnerCallbacks):
             utils.write_tree_file(self.options.tree, host, utils.jsonify(result2,format=True))
     
     def on_file_diff(self, host, diff):
-        if self.options.diff:
         print utils.get_diff(diff)
         super(CliRunnerCallbacks, self).on_file_diff(host, diff)