Merge pull request #17 from Azure/avagraw/test_util_updates

Upgrade alpine and node version

Dockerfile.amd64

@@ -1,4 +1,4 @@
-FROM node:8-alpine
+FROM node:15-alpine
 
 WORKDIR /app/
 

Dockerfile.arm32v7

@@ -1,4 +1,4 @@
-FROM arm32v7/node:8-slim
+FROM arm32v7/node:15-slim
 
 WORKDIR /app/
 

Dockerfile.arm64v8

@@ -1,4 +1,4 @@
-FROM arm64v8/node:8-slim
+FROM arm64v8/node:15-slim
 
 WORKDIR /app/