Add nfs-common package to the Ubuntu and Debian definitions

I like the Opscode boxes and I use them a lot, but I've had troubles lately because for some projects I need better shared directories' perfomance. With the NFS shared disrectories it is much better but the Opscode boxes (unlike the original Veewee ones) miss of the nfs client.

I've noticed that there is already a ticket for this, [BENTO-5](http://tickets.opscode.com/browse/BENTO-5), but the pull-request just cover the CENTOS boxes. This will cover the Debian and Ubuntu ones.

I would love to see this merged too.

Thanks