Fixed add_bootstrap_class template filter

Made sure that the add_bootstrap_class filter correctly obtains the
widget type to prevent it applying the form-control css class onto
parts of forms that shouldn't have it.

Change-Id: I307780b241e70de38e405cbffc4a35859b9aaf1b
Closes-Bug: 1367302
Merge "Fixed add_bootstrap_class template filter"