tests do not pass following installation instructions on CentOS 7.4 with stock kernel

From user report on mailing list, following our installation instructions on a CentOS 7.4 VM using the stock kernel and Red Hat's instructions to enable user namespaces in it (that we link to) results in non-passing tests because Docker fails. For example:

$ cd ~/charliecloud $ sudo docker build -t hello -f examples/serial/hello/Dockerfile . Sending build context to Docker daemon 3.639 MB Step 1/4 : FROM debian:jessie ---> 25fc9eb3417f Step 2/4 : RUN apt-get update && apt-get install -y openssh-client && rm -rf /var/lib/apt/lists/* ---> Using cache ---> c9a70c27702f Step 3/4 : COPY examples/serial/hello hello Error processing tar file(exit status 1): Container ID 1000 cannot be mapped to a host ID

It is not clear to me whether this is a documentation or code problem.