Add l3 attribute to network

The fix is to add l3 attribute(s) to the returned objects in get_network() and get_networks()

Fixes: bug #1180971
Change-Id: I4b9c932fae90a169ad1c0119f45e90a2ee260acd
(cherry picked from commit eb6182fa6192b1ae4268ac02583622978d449a09)
Merge "Add l3 attribute to network" into stable/grizzly