Update Makefile to use containerized tools.

Also added lint-dockerfile target.
Also added mod-update target to simplify updating mod dependencies in a way that will pass in Jenkins.
Also made minor changes to make Dockerfile pass hadolint.

VOL-2428

Change-Id: I62e0f7bcee929df24979c2dfa5c98eca36dd9cc4
diff --git a/docker/Dockerfile.openolt b/docker/Dockerfile.openolt
index 25f98f7..60d5b2c 100644
--- a/docker/Dockerfile.openolt
+++ b/docker/Dockerfile.openolt
@@ -18,7 +18,7 @@
 FROM golang:1.12-alpine3.9 AS build-env
 
 # Install required packages
-RUN apk add --no-cache wget git make build-base protobuf protobuf-dev
+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
 
 # Prepare directory structure
 WORKDIR /go/src