agent.pb.go is unchanged, but the files in networkdb and drivers
are slightly different when regenerated using the current versions
of protoc and gogoproto. This is probably because agent.pb.go
was last regenerated quite recently, in February 2018, whereas
networkdb.pb.go and overlay/overlay.pb.go were last changed in 2017,
and windows/overlay/overlay.pb.go was last changed in 2016.
Signed-off-by: Euan Harris <euan.harris@docker.com>
