Add more fixed ips

Go from 256 to 4096 fixed IP addresses.

The large ops test spins up 3 sets of instances then deletes them all at
the end. We are working on bumping the large-ops number up from 50 to
175, so we will need at least 525 fixed ip addresses.

Change-Id: Ie6cfd6e191ec873e577166e33e94b5996190a1c2
Merge "Add more fixed ips"