exit if not running as root

[hellt]

# first run without sudo as a regular user
[test@srl-centos7 ~]$ /tmp/container-lab
containerlab requires sudo privileges to run!

# now with sudo
[test@srl-centos7 ~]$ sudo /tmp/container-lab

We trust you have received the usual lecture from the local System
Administrator. It usually boils down to these three things:

    #1) Respect the privacy of others.
    #2) Think before you type.
    #3) With great power comes great responsibility.

[sudo] password for test:
deploy container based lab environments with a user-defined interconnections

Usage:
  containerlab [command]

Available Commands:
  config      generate and apply configuration to the lab

also ensured that deploy/destroy cmds work

close #105