dlm: Replace default_attrs in dlm_ktype with default_groups

The kobj_type default_attrs field is being replaced by the
default_groups field, so replace the default_attrs field in dlm_ktype
with default_groups. Use the ATTRIBUTE_GROUPS macro to create
dlm_groups.

Signed-off-by: Kimberly Brown <kimbrownkd@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>