Address scope is mutable on subnetpool after subnets were allocated.
When address scope changes, neutron fires AFTER_CHANGE event. Upon
catching this notification:
1. Log warning if no-nat router resulted with mixed address scopes
2. Recalculate snat rules if needed
3. Recalculate firewall rules
A fix for nsx-v3 was already introduced in commit
I1de25868db0d77fbcb7ebc588c6ab9493a3dadf4
Change-Id: I2696f0ba0edf0409993455b7a9e6e478383f3276
345e5ea10b