neutron-dhcp-agent can not be started when end user only use linuxbridge as l2 agent

[Yang Yu]

When we only install neutron-linuxbridge-agent package on RHEL6.5, the dhcp agent can not be started successfully. That is because there is hard code to use openvswitch.common plugin in nuetron.agent.linux.ovs_lib.py.

[root@osee15-control01 neutron]# /usr/bin/neutron-dhcp-agent --log-file /var/log/neutron/dhcp-agent.log --config-file /etc/neutron/neutron.conf --config-file /etc/neutron/dhcp_agent.ini
Traceback (most recent call last):
  File "/usr/bin/neutron-dhcp-agent", line 6, in <module>
    from neutron.agent.dhcp_agent import main
  File "/usr/lib/python2.6/site-packages/neutron/agent/dhcp_agent.py", line 27, in <module>
    from neutron.agent.linux import interface
  File "/usr/lib/python2.6/site-packages/neutron/agent/linux/interface.py", line 26, in <module>
    from neutron.agent.linux import ovs_lib
  File "/usr/lib/python2.6/site-packages/neutron/agent/linux/ovs_lib.py", line 31, in <module>
    from neutron.plugins.openvswitch.common import constants
ImportError: No module named openvswitch.common

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: master
Review: https://review.openstack.org/68344

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/115162

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/115162
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=65dde5624bbe1a1f896fe437fef0ad9bbe168153
Submitter: Jenkins
Branch: master

commit 65dde5624bbe1a1f896fe437fef0ad9bbe168153
Author: Prasoon Telang <email address hidden>
Date: Fri Aug 29 19:25:35 2014 +0530

    remove explicit include of the ovs plugin

    On installing only neutron-linuxbridge-agent package, the
    dhcp cannot start successfully because of the imports from
    ovs plugin. This change removes the explicit include of the
    ovs plugin from ovs_lib.py. INVALID_OFPORT has been moved to
    ovs_lib.py while VXLAN_UDP_PORT has moved to
    plugins/common/constants.py. The imports for these 2 constants
    in files which uses it has been corrected to new location.

    Closes-Bug: #1271449
    Change-Id: I6559cb43d1b10b4f926c453a103b12017b59f259