Host route to metadata server with Bigswitch/Floodlight Plugin

Host route to metadata server was not getting propagated
to VM when using the Big Switch/Floodlight plugin. The
reason being the update to the subnet (with the host
route information) was not being picked up by the dhcp
agent. This is being fixed here by sending a notification
to the dhcp agent when the host route is added to the subnet.

Fixes: Bug #1134043

Change-Id: If040f51946bcb734da319249df17d03e68aa5588
Move network schedule to first port creation.

blueprint quantum-scheduler

we remove scheduling network
to dhcp agent when creating network so that we can give admin
the chance to allocate the given network to a given dhcp agent after
network creation.

Change-Id: I228870669825405277de0505a3f2ece074918524
Merge "Move network schedule to first port creation."
Merge "Host route to metadata server with Bigswitch/Floodlight Plugin"