VIF Binding and Unbinding Mechanism

Action Items :-

 create the veth pair
 create the namespace
 Put one end to the namespace and then hand over the other veth to the vif-binding infrastructure (port-type dependant)

We would have -

/usr/libexec/kuryr/bind/name_of_port_type
/usr/libexec/kuryr/unbind/name_of_port_type

Name of port type could be `midonet`, `ovs`, etc.
Eachdriver would have an executable that receives the name of the veth pair that has to be bound to the overlay and the UUID of the Neutron port.
The other pair will be put by kuryr on the container namespace
If binding fails, i.e. it can fail to find the proper bind executable, it should lead to rollback of the top level operation.
     Otherwise there will be unbound port and no connectivity.

I have added etherpad link in specification, if you want to see full details click on "Read the full specification".
Here is etherpad link - https://etherpad.openstack.org/p/Kuryr_vif_binding_unbinding