utils: Confirm that Steam itself is running before talking to steam.pipe

It's possible for another process to have inherited the open steam.pipe fd and be continue holding it open after Steam itself exited, in which case trying to communicate with steam.pipe won't actually work. This adds a check before opening it to make sure Steam itself, not a child, is running, by getting the process from steam.pid and making sure it has steam.pipe open (i.e. the PID wasn't reused).

steamrt/tasks#529

Signed-off-by: Ryan Gonzalez ryan.gonzalez@collabora.com