Minor fix to Install and configure proxy node section

Changed "auth_port = 35357" to "auth_uri = http://controller:5000" as mentioned here: http://docs.openstack.org/trunk/install-guide/install/apt/content/neutron-install.dedicated-network-node.html

backport: none
Closes_Bug: #1327030

Change-Id: I362cf3e2f924a13e5bc3ea52ae41331b442dbf23
Merge "Minor fix to Install and configure proxy node section"