Fix warning message when running snap on some distros.
Fix warning message when running snap on some distros.

Debian & Ubuntu have /etc/lsb-release file which contains the release
info. On some distros, the file doesn't exist, Fedora has
/etc/fedora-release instead and /etc/os-release for opensuse. We check
if the file exists before we proceed for platform detection.

docker-snap/docker,docker-snap/docker,infosiftr/snap-docker