dlm: fix invalid free

[ Upstream commit d968b4e240cfe39d39d80483bac8bca8716fd93c ]

dlm_config_nodes() does not allocate nodes on failure, so we should not
free() nodes when it fails.

Signed-off-by: Tycho Andersen <tycho@tycho.ws>
Signed-off-by: David Teigland <teigland@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>