Fix typo in multinode-lab document
Fix typo in multinode-lab document

Signed-off-by: Nobuhiro MIKI <dbea52c4c908d186902f1b1eb90fdb4b56b97ad2@yahoo-corp.jp>
Change-Id: I1b6100d6b8231f1f96a7768e26ab83f010f1e4dc

openstack-dev/devstack,nawawi/openstack,openstack-dev/devstack,nawawi/openstack