Dockerfile: Swtich from dl-4 to dl-cdn.alpinelinux.org

* At the time of this commit dl-4.alpinelinux.org was unreachable.
* Switch to the CDN instead of some hardcoded server.

Author: kylemanna

Dockerfile

@@ -5,8 +5,10 @@ FROM alpine:3.5
 
 MAINTAINER Kyle Manna <[email protected]>
 
-RUN echo "http://dl-4.alpinelinux.org/alpine/edge/community/" >> /etc/apk/repositories && \
-    echo "http://dl-4.alpinelinux.org/alpine/edge/testing/" >> /etc/apk/repositories && \
+# Community: google-authenticator
+# Testing: pamtester
+RUN echo "http://dl-cdn.alpinelinux.org/alpine/edge/community/" >> /etc/apk/repositories && \
+    echo "http://dl-cdn.alpinelinux.org/alpine/edge/testing/" >> /etc/apk/repositories && \
     apk add --update openvpn iptables bash easy-rsa openvpn-auth-pam google-authenticator pamtester && \
     ln -s /usr/share/easy-rsa/easyrsa /usr/local/bin && \
     rm -rf /tmp/* /var/tmp/* /var/cache/apk/* /var/cache/distfiles/*