Cann't use extra-dhcp-opt to set networking parameters on stateless-dhcp network

[lee jian]

when using slaac+stateless dhcpv6 to configure ipv6 address and networking configurations on OpenStack， if the network only consist one ipv6 subnet with ipv6-address-mode setted as stateless-dhcpv6，the dhcp agent will filter this subnet in its _iter_hosts() function, at this time, even you use extr-dhcp-opt to set network configuration on ports of this subnet, they will not be included in the host file of the dnsmasq, and can not be got through dhcpv6 protocal. The stateless dhcpv6 will fail on this situation!

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/147455

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/147455
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=a584e35775391a2a93535482c5a05ff8774cb56b
Submitter: Jenkins
Branch: master

commit a584e35775391a2a93535482c5a05ff8774cb56b
Author: lijianlj <email address hidden>
Date: Fri Jan 16 17:02:40 2015 +0800

    Fix extra-dhcp-opt on stateless dhcpv6 subnet

    The opts in dnsmasq opt-file is depending on the tag set
    in the host-file. When you have only one stateless dhcpv6 subnet,
    it will be filtered by the _iter_host() function, and will not be
    written to the host-file, this may lead to extra-dhcp-opt not working.

    Closes-Bug:#1411137

    Change-Id: Ieed16280fb3c4c91f7d906c0410446d2a112b93e

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/juno
Review: https://review.openstack.org/153181

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/153181
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=41bfc2fbd15b75176376af56c80b1d6686695a3d
Submitter: Jenkins
Branch: stable/juno

commit 41bfc2fbd15b75176376af56c80b1d6686695a3d
Author: lijianlj <email address hidden>
Date: Fri Jan 16 17:02:40 2015 +0800

    Fix extra-dhcp-opt on stateless dhcpv6 subnet

    The opts in dnsmasq opt-file is depending on the tag set
    in the host-file. When you have only one stateless dhcpv6 subnet,
    it will be filtered by the _iter_host() function, and will not be
    written to the host-file, this may lead to extra-dhcp-opt not working.

    Closes-Bug:#1411137

    Conflicts:
     neutron/agent/linux/dhcp.py
     neutron/tests/unit/test_linux_dhcp.py

    Change-Id: Ieed16280fb3c4c91f7d906c0410446d2a112b93e
    (cherry picked from commit a584e35775391a2a93535482c5a05ff8774cb56b)