[c-nsp] route-target import on non-leaking PEs

[Adam Vitkovsky]

> In my case, I've always used a common RD, import and export RT inside any
given VRF. 
Using common RD in a vrf is asking for trouble if route-reflection is used.

Let's say you have two PEs advertising default for vrf inet -if you use RRs
to spread the routes throughout the backbone -RRs will only advertise one
(best path)default route to all PEs. 
Now with unique RD per PE RRs will consider default form each PE as a unique
route sending both to all PEs. 
Than you are ready for fast convergence. 
adam