Merge pull request #2946 from mjstapp/dplane_2

Zebra: async dataplane, phase 1

diff --cc zebra/kernel_socket.c
Simple merge

diff --cc zebra/main.c
Simple merge

diff --cc zebra/zapi_msg.c
Simple merge

diff --cc zebra/zebra_rib.c
Simple merge

diff --cc zebra/zebra_rnh.c
Simple merge

diff --cc zebra/zebra_vty.c
Simple merge