DHCP router option is not sent when classless router option is sent

[Hari Prasad Killi]

RFC3441 says:

   Many clients may not implement the Classless Static Routes option.
   DHCP server administrators should therefore configure their DHCP
   servers to send both a Router option and a Classless Static Routes
   option, and should specify the default router(s) both in the Router
   option and in the Classless Static Routes option.

   When a DHCP client requests the Classless Static Routes option and
   also requests either or both of the Router option and the Static
   Routes option, and the DHCP server is sending Classless Static Routes
   options to that client, the server SHOULD NOT include the Router or
   Static Routes options.

[Hari Prasad Killi (haripk)]

Fixed with https://github.com/Juniper/contrail-controller/commit/1d1057082e5f173c35d6fc9b6b03c7ad8f527ecc