Merge pull request #573 from prashanth26/update/docker-images

Update docker images to use latest gcr copy

Author: prashanth26

Dockerfile

@@ -1,13 +1,13 @@
 #############      builder                                  #############
-FROM golang:1.13.5 AS builder
+FROM eu.gcr.io/gardener-project/3rd/golang:1.15.5 AS builder
 
 WORKDIR /go/src/github.com/gardener/machine-controller-manager
 COPY . .
 
 RUN .ci/build
 
 #############      base                                     #############
-FROM alpine:3.11.2 as base
+FROM eu.gcr.io/gardener-project/3rd/alpine:3.12.1 as base
 
 RUN apk add --update bash curl tzdata
 WORKDIR /