neutron boot error because PUBLIC_BRIDGE not defined

[yalei wang]

when setting the linuxbridge as Q_AGENT in local.conf, error will emit because the PUBLIC_BRIDGE not be set.

Q_AGENT=linuxbridge

====================================
2015-05-13 09:54:01.935 | ++ read data
2015-05-13 09:54:01.935 | + local ipv6_pub_subnet_id=f6c49b40-62fc-474e-b58d-35f190036193
2015-05-13 09:54:01.935 | + [[ 4+6 == \6 ]]
2015-05-13 09:54:01.935 | + is_service_enabled q-l3
2015-05-13 09:54:01.936 | + return 0
2015-05-13 09:54:01.936 | + sudo sysctl -w net.ipv6.conf.all.forwarding=1
2015-05-13 09:54:01.939 | net.ipv6.conf.all.forwarding = 1
2015-05-13 09:54:01.940 | ++ neutron port-list -c fixed_ips
2015-05-13 09:54:01.940 | ++ awk -F '"' -v subnet_id=f6c49b40-62fc-474e-b58d-35f190036193 '$4 == subnet_id { print $8; }'
2015-05-13 09:54:01.940 | ++ grep f6c49b40-62fc-474e-b58d-35f190036193
2015-05-13 09:54:02.445 | + IPV6_ROUTER_GW_IP=2001:db8::1
2015-05-13 09:54:02.445 | + die_if_not_set 1295 IPV6_ROUTER_GW_IP 'Failure retrieving IPV6_ROUTER_GW_IP'
2015-05-13 09:54:02.445 | + local exitcode=0
2015-05-13 09:54:02.446 | + sudo sysctl -w net.ipv6.conf..disable_ipv6=1
2015-05-13 09:54:02.449 | error: "net.ipv6.conf..disable_ipv6" is an unknown key
2015-05-13 09:54:02.450 | + exit_trap
2015-05-13 09:54:02.450 | + local r=255
2015-05-13 09:54:02.450 | ++ jobs -p
2015-05-13 09:54:02.450 | + jobs=
2015-05-13 09:54:02.450 | + [[ -n '' ]]
2015-05-13 09:54:02.450 | + kill_spinner
2015-05-13 09:54:02.450 | + '[' '!' -z '' ']'
2015-05-13 09:54:02.450 | + [[ 255 -ne 0 ]]
2015-05-13 09:54:02.450 | + echo 'Error on exit'
2015-05-13 09:54:02.450 | Error on exit
2015-05-13 09:54:02.450 | + [[ -z /opt/stack/logs ]]
2015-05-13 09:54:02.450 | + /opt/stack/job/devstack_new/tools/worlddump.py -d /opt/stack/logs
2015-05-13 09:54:02.498 | + exit 255

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/182534

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/182534
Committed: https://git.openstack.org/cgit/openstack-dev/devstack/commit/?id=75c44737121baea0c56050599350bc7de8f22799
Submitter: Jenkins
Branch: master

commit 75c44737121baea0c56050599350bc7de8f22799
Author: Yalei Wang <email address hidden>
Date: Wed May 13 12:43:56 2015 +0800

    Remove the code against flushing public bridge

    As unstack.sh does destroy all bridges, we don't have to refresh bridge
    interface any more, as what is done in commit
    c2dc95add6e46829f1705041c1d9dddab9b360d3. So in this commit we will continue to
    remove the related statements in lib/neutron-legacy. These statements will also
    cause undefined PUBLIC_BRIDGE error.

    Change-Id: I4c7617f6a245ea4e2e08f518d873b1b8adc2b807
    Closes-Bug: #1454475