Add script to restore DNS server settings to the original DNS settings.

This script will restore the DNS server settings to the original DNS settings
discarding the DNS servers proposed by the VPN client.
This can be useful in cases where the DNS servers proposed by the VPN client
are not accessible over the VPN connection.

Signed-off-by: Gert Hulselmans <hulselmansgert@gmail.com>
Merge pull request #3 from ghuls/restore-original-dns

Add sample script to restore DNS server settings to the original DNS settings.