- Changes are no longer erroneously reported on RHEL (#12)
- Adding new link groups on Debian works again.
- This was broken in a previous commit by assuming the OS was RHEL
if `update-alternatives --query <name>` had a return code of 2
- Prefer `--display` over `--query` for determining available
alternatives
- --display is more distro-agnostic and simplifies the code
- Fix missing `msg=` in `fail_json` call when `link` is missing
- Document that `link` is required on RHEL-based distros
Tested on Ubuntu 12.04+ and CentOS 6/7
RedHat-based OSes have a version of update-alternatives which comes from
the chkconfig package and does not support the --query parameter. Work
around that.
