dlm: return -ENOMEM if ls_recover_buf fails

This patch fixes to return -ENOMEM in case of an allocation failure that
was forgotten to change in commit 6c648035 ("dlm: switch to use
rhashtable for rsbs").

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/r/202404200536.jGi6052v-lkp@intel.com/


Fixes: 6c648035 ("dlm: switch to use rhashtable for rsbs")
Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>