Corrects commands.
Corrects commands.

This patch removes the redundant "--" in some commands in DNS
integration in OpenStack Networking guide.

Change-Id: Ie0823302ec2ddb9e5957a4e81ff90863a846d105

AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals