Patch as-is resulted in traceback:

2015-04-16 19:16:24.496 58732 TRACE neutron.plugins.linuxbridge.agent.linuxbridge_neutron_agent Traceback (most recent call last):
2015-04-16 19:16:24.496 58732 TRACE neutron.plugins.linuxbridge.agent.linuxbridge_neutron_agent   File "/usr/local/lib/python2.7/dist-packages/neutron/plugins/linuxbridge/agent/linuxbridge_neutron_agent.py", line 1014, in daemon_loop
2015-04-16 19:16:24.496 58732 TRACE neutron.plugins.linuxbridge.agent.linuxbridge_neutron_agent     sync = self.process_network_devices(device_info)
2015-04-16 19:16:24.496 58732 TRACE neutron.plugins.linuxbridge.agent.linuxbridge_neutron_agent   File "/usr/local/lib/python2.7/dist-packages/neutron/plugins/linuxbridge/agent/linuxbridge_neutron_agent.py", line 870, in process_network_devices
2015-04-16 19:16:24.496 58732 TRACE neutron.plugins.linuxbridge.agent.linuxbridge_neutron_agent     resync_a = self.treat_devices_added_updated(devices_added_updated)
2015-04-16 19:16:24.496 58732 TRACE neutron.plugins.linuxbridge.agent.linuxbridge_neutron_agent   File "/usr/local/lib/python2.7/dist-packages/neutron/plugins/linuxbridge/agent/linuxbridge_neutron_agent.py", line 910, in treat_devices_added_updated
2015-04-16 19:16:24.496 58732 TRACE neutron.plugins.linuxbridge.agent.linuxbridge_neutron_agent     device_details['port_id']):
2015-04-16 19:16:24.496 58732 TRACE neutron.plugins.linuxbridge.agent.linuxbridge_neutron_agent   File "/usr/local/lib/python2.7/dist-packages/neutron/plugins/linuxbridge/agent/linuxbridge_neutron_agent.py", line 435, in add_interface
2015-04-16 19:16:24.496 58732 TRACE neutron.plugins.linuxbridge.agent.linuxbridge_neutron_agent     tap_device_name)
2015-04-16 19:16:24.496 58732 TRACE neutron.plugins.linuxbridge.agent.linuxbridge_neutron_agent   File "/usr/local/lib/python2.7/dist-packages/neutron/plugins/linuxbridge/agent/linuxbridge_neutron_agent.py", line 401, in add_tap_interface
2015-04-16 19:16:24.496 58732 TRACE neutron.plugins.linuxbridge.agent.linuxbridge_neutron_agent     self.ensure_tap_mtu(tap_device_name, phy_dev_name)
2015-04-16 19:16:24.496 58732 TRACE neutron.plugins.linuxbridge.agent.linuxbridge_neutron_agent   File "/usr/local/lib/python2.7/dist-packages/neutron/plugins/linuxbridge/agent/linuxbridge_neutron_agent.py", line 425, in ensure_tap_mtu
2015-04-16 19:16:24.496 58732 TRACE neutron.plugins.linuxbridge.agent.linuxbridge_neutron_agent     ip_lib.IPDevice(tap_dev_name).link.set_mtu(phy_dev_mtu)
2015-04-16 19:16:24.496 58732 TRACE neutron.plugins.linuxbridge.agent.linuxbridge_neutron_agent   File "/usr/local/lib/python2.7/dist-packages/neutron/agent/linux/ip_lib.py", line 258, in set_mtu
2015-04-16 19:16:24.496 58732 TRACE neutron.plugins.linuxbridge.agent.linuxbridge_neutron_agent     self._as_root('set', self.name, 'mtu', mtu_size)
2015-04-16 19:16:24.496 58732 TRACE neutron.plugins.linuxbridge.agent.linuxbridge_neutron_agent   File "/usr/local/lib/python2.7/dist-packages/neutron/agent/linux/ip_lib.py", line 242, in _as_root
2015-04-16 19:16:24.496 58732 TRACE neutron.plugins.linuxbridge.agent.linuxbridge_neutron_agent     kwargs.get('use_root_namespace', False))
2015-04-16 19:16:24.496 58732 TRACE neutron.plugins.linuxbridge.agent.linuxbridge_neutron_agent   File "/usr/local/lib/python2.7/dist-packages/neutron/agent/linux/ip_lib.py", line 65, in _as_root
2015-04-16 19:16:24.496 58732 TRACE neutron.plugins.linuxbridge.agent.linuxbridge_neutron_agent     raise exceptions.SudoRequired()
2015-04-16 19:16:24.496 58732 TRACE neutron.plugins.linuxbridge.agent.linuxbridge_neutron_agent SudoRequired: Sudo privilege is required to run this command.

Changing line 416 to include root helper allowed it to work as expected:

>> ip_lib.IPDevice(tap_dev_name).link.set_mtu(phy_dev_mtu)

   def ensure_tap_mtu(self, tap_dev_name, phy_dev_name):
        """Ensure the MTU on the tap is the same as the physical device."""
        phy_dev_mtu = ip_lib.IPDevice(phy_dev_name).link.mtu
        ip_lib.IPDevice(tap_dev_name, self.root_helper).link.set_mtu(phy_dev_mtu)