Reduce OneDocker runtime permissions (#2311)

Summary:
Pull Request resolved: #2311

This change updates OneDocker image runtime to use a non-root user, with limited permissions. This is necessary for security isolation.

Reviewed By: musebc

Differential Revision: D46566033

fbshipit-source-id: 653b9b6a46f3b2070a647abd6d161a904fb60610

docker/onedocker/prod/Dockerfile.ubuntu

@@ -63,4 +63,7 @@ ENV WRITE_ROUTING_SCRIPT="/home/onedocker/package/write_routing.sh"
 RUN echo "%${caAdminGroup} ALL=(ALL) NOPASSWD: ${WRITE_ROUTING_SCRIPT}" >> /etc/sudoers
 
 CMD ["/bin/bash"]
+
+# Switch to non-root user for security purposes
+USER onedocker
 WORKDIR /home/onedocker