detects if VPN connection is present on Mac/Linux.
Split 'common/' into commit '59e1970ae7ab048c038dbab7b3e74f25ad66a59e'

git-subtree-dir: common
git-subtree-mainline: 2b1d79417c6e87c097caa5431bd92be97e0280b3
git-subtree-split: 59e1970ae7ab048c038dbab7b3e74f25ad66a59e