Allow access to metadata service

We need to allow access to the nova metadata service on port 8775,
having the port blocked was ok, in cases where the requests came
in on port 80 and then routed to port 8775 (with iptables) but didn't
work in cases where the source is NAT'd in the conpute host

Change-Id: Ie95eac27160df6aefa6b208cef5ebe316e0953f6