Add hook for network info update

This hook will allow deployers to register scripts that will
be called whenever an instance's network information is updated.
Scripts will be called with original arguments of the network
info update function call.

Implements: bp instance-network-info-hook

Change-Id: I56ff28d305cf8d9a67b37c45062256b3899f11dd
Merge "Add hook for network info update"