[FEATURE] SteamCMD lock update

[BlackYuzia]

Short

I use crontab for auto updates by update command.
But, if I manualy update server and in this moment was ran crontab task with update, we get two updates tasks.

Suggestion

Add a lock file (or any else lock) for prevent double update/validate etc dedicated servers per once.

[dgibbs64]

CLosing as I belive there is a lock now that prevents update runnign twice