Remove and recreate interface if already exists

If the dhcp-agent machine restarts when openvswitch comes up it logs the
following warning messages for all tap interfaces that do not exist:

bridge|WARN|could not open network device tap2cf7dbad-9d (No such device)

Once the dhcp-agent starts it recreates the interfaces and re-adds them to the
ovs-bridge. Unfortunately, ovs does not reinitialize the interfaces as they
are already in ovsdb and does not assign them a ofport number.

This situation corrects itself though the next time a port is added to the
ovs-bridge which is why no one has probably noticed this issue till now.

In order to correct this we should first remove interface that exist and
then readd them.

Closes-bug: #1268762

Change-Id: I4bb0019135ab7fa7cdfa6d5db3bff6eafe22fc85
Use the Session cookies for authentication on ODL REST API
This patch uses the session cookies from the first successful request to authenticate ML2 against the ODL REST API.
This reduces the amount of logging on the ODL OSGI Console...
Remove support for binding ports on VLAN networks

OVSDB in ODL doesn't support VLAN networks yet, so remove this support from
the MechanismDriver binding code for now. We'll add this back if we ever
support VLANs in OVSDB+ODL.
Updated docstring format and fixed typos
Merge pull request #3 from dave-tucker/odl_ml2

Use the Session cookies for ODL REST API authentication
Merge branch 'odl_ml2' of github.com:CiscoSystems/neutron into odl_ml2
Merge branch 'master' of git://git.openstack.org/openstack/neutron into odl_ml2
Fix unneeded whitespace issues.

Change-Id: I41e7e4b355209c638d769fcefad89646a2509170
Reverse DB migration patch

Fix a previous DB migration issue in preparation for upstreaming the ODL
MechanismDriver.

Change-Id: Ie4398ca1ee445217b3c69b13c7feaebaf1288704
Add back symbolic link

Change-Id: Id0928f11cba30c16c2bc88d4a709c94fb81f46f9