Comment 15 for bug 1383674

There is another strategy which could work, using OpenFlow cookies:

1) At agent boot, mark current flows with a cookie to make sure we can delete them later by reference.
2) Insert the new flows on the bridge,
3) Drop the old flows by cookie reference.

Ideally, if we recover the VLAN mapping from the openvswitch info at reboot, should not be
any conflicts between new and old rules.