update the dockerfile

samples/src/helloworld/windows/Dockerfile

@@ -1,2 +1,12 @@
-FROM microsoft/aspnet:4.7.1-windowsservercore-1709
-COPY . /inetpub/wwwroot
+FROM microsoft/iis:windowsservercore-1709
+
+RUN mkdir C:\site
+
+RUN powershell -NoProfile -Command \
+    Import-module IISAdministration; \
+    Remove-WebSite -Name 'Default Web Site'; \
+    New-IISSite -Name "Site" -PhysicalPath C:\site -BindingInformation "*:80:"
+
+EXPOSE 80
+
+ADD . /site