Optimize network sync
Optimize network sync

If a network is not going to be changed, then we don't want to hold on
to its plenary object, to avoid locking overhead.

Change-Id: Ie722a0d108ed652e4f31256117a41d06e669017e
Reviewed-by: Dave Reeve <6a84ee3ae0690d4584b99406fb3076392171f50e@morganstanley.com>

quattor/aquilon,guillaume-philippon/aquilon,guillaume-philippon/aquilon,guillaume-philippon/aquilon,quattor/aquilon,quattor/aquilon