DHCP: when upgrading from icehouse DHCP breaks

[Gary Kotton]

When upgrading the J, K or any other version the DNS support break.
That is, the DHCP agent has the option for setting DNS servers, this is via the the options dnsmasq_config_file=/etc/neutron/myconfig.ini
Where myconfig will have support for the following:
dhcp-option=5,2.4.5.6,2.4.5.7
dhcp-option=6,2.4.5.7,2.4.5.6

In the guest /etc/resolve.conf we see the DHCP address and not the configured IP's

The reason for this is https://github.com/openstack/neutron/commit/3686d035ded94eadab6a3268e4b0f0cca11a22f8

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/275267

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/275267
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=13a4268062b17fbb6451e53632297c8e06c45a51
Submitter: Jenkins
Branch: master

commit 13a4268062b17fbb6451e53632297c8e06c45a51
Author: Gary Kotton <email address hidden>
Date: Tue Feb 2 07:26:48 2016 -0800

    DHCP: fix regression with DNS nameservers

    The commit 3686d035ded94eadab6a3268e4b0f0cca11a22f8 caused a
    regression for setups that support a number of DNS servers that
    are injected via the DHCP options 5 and 6.

    If the dnsmaq has a configured dns-server then it will ignore
    the ones that are injected by the admin. That is what the commit
    above did. This causes a number of problems. The main one is that
    it requires the DHCP agent to have connectivity to the DNS server.

    The original code was added in commit
    2afff147c45f97a0809db40ad072332fb37ccd8d

    Change-Id: Iae3e994533102a2b076cc2dc205cdd5caaee1206
    Closes-bug: #1540960

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/liberty
Review: https://review.openstack.org/276794

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/276794
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=b2afdb0e01c5bdb79c0ad59832fc18c1934f910d
Submitter: Jenkins
Branch: stable/liberty

commit b2afdb0e01c5bdb79c0ad59832fc18c1934f910d
Author: Gary Kotton <email address hidden>
Date: Tue Feb 2 07:26:48 2016 -0800

    DHCP: fix regression with DNS nameservers

    The commit 3686d035ded94eadab6a3268e4b0f0cca11a22f8 caused a
    regression for setups that support a number of DNS servers that
    are injected via the DHCP options 5 and 6.

    If the dnsmaq has a configured dns-server then it will ignore
    the ones that are injected by the admin. That is what the commit
    above did. This causes a number of problems. The main one is that
    it requires the DHCP agent to have connectivity to the DNS server.

    The original code was added in commit
    2afff147c45f97a0809db40ad072332fb37ccd8d

    Change-Id: Iae3e994533102a2b076cc2dc205cdd5caaee1206
    Closes-bug: #1540960
    (cherry picked from commit 13a4268062b17fbb6451e53632297c8e06c45a51)