Get dockerize from Git instead of Alpine repository

Dockerfile.alpine

@@ -4,10 +4,14 @@ FROM alpine:3.7
 VOLUME /data
 VOLUME /config
 
-RUN echo "@testing http://dl-cdn.alpinelinux.org/alpine/edge/testing" >> /etc/apk/repositories \
-    && apk --no-cache add dockerize@testing dumb-init openvpn shadow transmission-daemon \
+ENV DOCKERIZE_VERSION=v0.6.0
+RUN apk --no-cache add dumb-init openvpn shadow transmission-daemon \
+    && echo "Install dockerize $DOCKERIZE_VERSION" \
+    && wget -qO- https://github.com/jwilder/dockerize/releases/download/$DOCKERIZE_VERSION/dockerize-linux-amd64-$DOCKERIZE_VERSION.tar.gz | tar xz -C /usr/bin \
     && mkdir -p /opt/transmission-ui/combustion-release /opt/transmission-ui/kettu \
+    && echo "Install Combustion" \
     && wget -qO- https://github.com/Secretmapper/combustion/archive/release.tar.gz | tar xz -C /opt/transmission-ui \
+    && echo "Install kettu" \
     && wget -qO- https://github.com/endor/kettu/archive/master.tar.gz | tar xz -C /opt/transmission-ui/kettu \
     && rm -rf /tmp/* /var/tmp/* \
     && groupmod -g 1000 users \