provision: update /etc/sudoers restoration mechanism
provision: update /etc/sudoers restoration mechanism

With this commit, /etc/sudoers is always restored when SIGHUP, SIGINT,
SIGTERM or SIGSTOP is received. Robustness improved.

zmwangx/dotfiles,zmwangx/dotfiles,zmwangx/dotfiles,zmwangx/dotfiles,zmwangx/dotfiles