Use voltha-protos version 4.0.2
Bump major version of voltha-lib-go to 4.0.0 as this change results
in incompatible API version compared to previous version

Change-Id: I1def58361fb1d85f07d6948ebf1ffb7a92eb0d4c
diff --git a/go.sum b/go.sum
index fe4e421..89312e8 100644
--- a/go.sum
+++ b/go.sum
@@ -196,8 +196,8 @@
 github.com/onsi/ginkgo v1.6.0/go.mod h1:lLunBs/Ym6LB5Z9jYTR76FiuTmxDTDusOGeTQH+WWjE=
 github.com/onsi/gomega v1.4.2 h1:3mYCb7aPxS/RU7TI1y4rkEn1oKmPRjNJLNEXgw7MH2I=
 github.com/onsi/gomega v1.4.2/go.mod h1:ex+gbHU/CVuBBDIJjb2X0qEXbFg53c61hWP/1CpauHY=
-github.com/opencord/voltha-protos/v3 v3.4.1 h1:Nrr0jKy7WiMiFlXYiK8z73RvI4K4L5b/top7d3htQQI=
-github.com/opencord/voltha-protos/v3 v3.4.1/go.mod h1:nl1ETp5Iw3avxOaKD8BJlYY5wYI4KeV95aT1pL63nto=
+github.com/opencord/voltha-protos/v4 v4.0.2 h1:SI25ljqftc8Tc28CgfqSE4IGCLJ5MgCmBQlE96hl9X8=
+github.com/opencord/voltha-protos/v4 v4.0.2/go.mod h1:W/OIFIyvFh/C0vchRUuarIsMylEhzCRM9pNxLvkPtKc=
 github.com/opentracing/opentracing-go v1.1.0 h1:pWlfV3Bxv7k65HYwkikxat0+s3pV4bsqf19k25Ur8rU=
 github.com/opentracing/opentracing-go v1.1.0/go.mod h1:UkNAQd3GIcIGf0SeVgPpRdFStlNbqXla1AfSYxPUl2o=
 github.com/pascaldekloe/goe v0.0.0-20180627143212-57f6aae5913c/go.mod h1:lzWF7FIEvWOWxwDKqyGYQf6ZUaNfKdP144TG7ZOy1lc=