docker/bootstrap: Update the Maven mirror to a more reliable one.

docker/bootstrap/Dockerfile.common

@@ -49,7 +49,7 @@ RUN mkdir -p /vt/bin && \
 RUN mkdir -p /vt/dist && \
     cd /vt/dist && \
     curl -sL --connect-timeout 10 --retry 3 \
-        http://www.carfab.com/apachesoftware/maven/maven-3/3.3.3/binaries/apache-maven-3.3.3-bin.tar.gz | tar -xz && \
+        http://www-us.apache.org/dist/maven/maven-3/3.3.3/binaries/apache-maven-3.3.3-bin.tar.gz | tar -xz && \
     mv apache-maven-3.3.3 maven
 
 # Install etcd v2.0