Added support for ufw

Changed /etc/default/ufw according to
http://docs.docker.com/installation/ubuntulinux/#docker-and-ufw

If the file /etc/default/ufw is not existent it will skip changing
the forward policy.
Merge pull request #13 from samos123/ufw-support

Added support for ufw
to fix ufw change bug
Merge pull request #14 from fupelaqu/master

to fix ufw change bug
Merge branch 'master' of github.com:angstwad/docker.ubuntu

Conflicts:
	tasks/main.yml