Comment 0 for bug 1526084

In DhcpAgent, when enable_isolated_metadata_proxy() spawns a metadata proxy agent
for a network, it will pass router_id instead of network_id if metadata network is enabled
and a router port is connected to this network. Later, MatadataDriver will register this uuid
(i.e. router_id) with monitor for the new metadata proxy process.

But when disable_isolated_metadata_proxy() destroys a metadata proxy agent for a network,
it always passes network_id as the uuid. Thus MatadataDriver can not find the matching process.
So the corresponding metadata proxy agent can not be destroyed.