Use cached nwinfo for secgroup rules

This stops a potential DOS with source security groups by using the
db cached version of the network info instead of calling out to
the network api multiple times.

Fixes bug 1184041

Change-Id: Id5f24ecf0e8cce60c27a9aecbc6e606c4c44d6b6
(cherry picked from commit 85aac04704350566d6b06aa7a3b99649946c672c)
Merge "Use cached nwinfo for secgroup rules" into stable/grizzly