shfiter does not allow entering the container as specific user

[rhaas80]

The shifter variant of docker for HPC systems does not support the -u option of docker and instead always runs programs inside of the container with the actual user ID of the current user.

Thus the files in /home/nanograv must be made world readable, in particular since shifter wipes /etc/passwd and replaces it with a version that contains only root and the user account of the user.