fix docker build by forcing older version of public_suffix

Author: gmenuel

docker/puppetserver/Dockerfile

@@ -89,6 +89,7 @@ RUN apt-get update && \
     git config --global user.email "[email protected]" && \
     chmod 0755 /usr/local/bin/lein && \
     /usr/local/bin/lein && \
+    gem install --no-doc public_suffix -v 4.0.7 && \
     gem install --no-doc bundler fpm
 
 COPY . /puppetserver