Updated tools version to 2.0.0

Also merged lint-style (gofmt) into golangci-lint (enabled gofmt).
Also removed redundant lint-sanity (govet) which is already checked by golangci-lint.
Also made minor code changes to pass new golangci-lint tests.
Also changed lint-mod slightly so it reverts any changes it makes go.mod, go.sum, and vendor/.

VOL-2647

Change-Id: I15557edf0f9225ea1c44e5bab29481d17a82e2b8
diff --git a/docker/Dockerfile.rw_core b/docker/Dockerfile.rw_core
index 6def3fa..76bc42e 100644
--- a/docker/Dockerfile.rw_core
+++ b/docker/Dockerfile.rw_core
@@ -15,16 +15,10 @@
 # -------------
 # Build stage
 
-FROM golang:1.12-alpine3.9 AS build-env
+FROM golang:1.13.8-alpine3.11 AS build-env
 
 # Install required packages
-RUN apk add --no-cache \
-	wget=1.20.3-r0 \
-	git=2.20.2-r0 \
-	make=4.2.1-r2 \
-	build-base=0.5-r1 \
-	protobuf=3.6.1-r1 \
-	protobuf-dev=3.6.1-r1
+RUN apk add --no-cache build-base=0.5-r1
 
 # Golang container has GOPATH set to /go by default. Hence, need to explicitly enable
 # Go modules while using folder /go/src under GOPATH as build path; lest go modules
@@ -67,7 +61,7 @@
 # -------------
 # Image creation stage
 
-FROM alpine:3.9.4
+FROM alpine:3.11.3
 
 # Set the working directory
 WORKDIR /app