Get DNS-IPv6 from current system resolvers

Allow IPv4 and IPv6 to get from resolv.conf.
Filter out commets by grepping "nameserver" from beginning of line. No additional comment filter need.
Replace multiple grep with single sed.

openvpn-install.sh

@@ -754,7 +754,7 @@ ifconfig-pool-persist ipp.txt" >> /etc/openvpn/server.conf
 				RESOLVCONF='/etc/resolv.conf'
 			fi
 			# Obtain the resolvers from resolv.conf and use them for OpenVPN
-			grep -v '#' $RESOLVCONF | grep 'nameserver' | grep -E -o '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' | while read -r line; do
+			sed -ne 's/^nameserver[[:space:]]\+\([^[:space:]]\+\).*$/\1/p' $RESOLVCONF | while read -r line; do
 				echo "push \"dhcp-option DNS $line\"" >> /etc/openvpn/server.conf
 			done
 		;;