Optimise nil checking in rendering structs to Notifications. (#302)
Optimise nil checking in rendering structs to Notifications. (#302)

* (M) ygot/render.go
  - Before this change, we calculate the paths that a field should be
    mapped to before we check whether it is nil or not, we can avoid
    doing any check of a struct field's path at all if we check whether
    it was nil *before*.
openconfig/ygot,openconfig/ygot