Weak/useless auth_tokens when run from macOS

[lattwood]

Issue

Any use of this role from a macOS machine without coreutils installed from Homebrew, with the PATH adjustment added (PATH="$HOMEBREW_PREFIX/opt/coreutils/libexec/gnubin:$PATH") will use BSD tr instead of GNU tr. The role uses tr to read 128 random printable characters from /dev/urandom, by using the -dc flags to remove anything not in the a-zA-Z0-9 character range.

This is an issue, because you can end up with single character auth_tokens.

Suggested Resolution

• Big warning in the README.md about this issue.
• Generate the auth_token on one node (guaranteed to be Linux) instead of delegating it to localhost.