Squashing following changes:
* Initial changes to support tcp communication between agent and vrouter
 - Config option to specify platform type(dpdk or nic)
 - exception interface to support unix socket and ethernet interface

* Bind on the netlink socket before sending, this change
  was missed in earlier commit resulting in sending of message before bind

* Allocate mpls label at steps of 16, so that flow directory
  can uniquely place the packet in per vm queue.

* Send ip address of vhost interface on physical interface, so that
  ip address can be programmed in flow director for physical interface

* Set os index as pci bus:slot:function, so that dpdk-vrouter can
  add the interface

* Read mac address of physical interface from config file.
* Wait for conection to vrouter to be complete before adding DB entries

* Dont look for tap interface in case of dpdk tap interface

* Reconnect with dpd-vrouter, if connect failed