Disbale DNS update for port o-hm0 in devstack
Disbale DNS update for port o-hm0 in devstack

Disable the DNS update for port o-hm0 during the installation of
devstack to aviod accidentally DNS change.

Note: NetworkManager will attempt to write DNS information from
DHCP into /etc/resolv.conf, overwriting the existing contents.
So, if you have NetworkManager enabled, the once for all solution
should be set the immutable bit on the file:
    chattr +i /etc/resolv.conf

Change-Id: Icbc23feb8cb3c9967aa66a3c6c2f61da61397d11

openstack/octavia,openstack/octavia,openstack/octavia