Prevent cross plugging router ports from other tenants

Previously, a tenant could plug an interface into another tenant's
router if he knew their router_id by creating a port with the correct
device_id and device_owner. This patch prevents this from occuring
by preventing non-admin users from creating ports with device_owner
network:router_interface with a device_id that matches another tenants router.
In addition, it prevents one from updating a ports device_owner and device_id
so that the device_id won't match another tenants router with device_owner
being network:router_interface.

NOTE: with this change it does open up the possiblity for a tenant to discover
router_id's of another tenant's by guessing them and updating a port till
a conflict occurs. That said, randomly guessing the router id would be hard
and in theory should not matter if exposed. We also need to allow a tenant
to update the device_id on network:router_interface ports as this would be
used for by anyone using a vm as a service router. This issue will be fixed in
another patch upstream as a db migration is required but since this needs
to be backported to all stable branches this is not possible.

NOTE: The only plugins affect by this are the ones that use the l3-agent.

NOTE: **One should perform and audit of the ports that are already
        attached to routers after applying this patch and remove ports
        that a tenant may have cross plugged.**

Change-Id: I8bc6241f537d937e5729072dcc76871bf407cdb3
Closes-bug: #1243327
Make dnsmasq aware of all names

Each dnsmasq instance on a network is not aware of other dnsmasq's leases.

When dnsmasq is launched with --no-hosts and is not provided an --addn-hosts
file, it can resolve only the hosts to which it gives a dhcp lease and no more.
i.e.:
If dnsmasq service n°1 gives a lease to instance n°1, and dnsmasq service n°2
gives a lease to instance n°2, both VM instances and dnsmasq services being on
the same network: instance n°1 can not resolve instance n°2, because instance
n°1 queries dnsmasq n°1, and since it did not give the lease to instance n°2,
it can not resolve it (it is not aware of its existence). Same issue if
instance n°2 tries to resolve instance n°1.

The solution is to provide dnsmasq with an --addn-hosts file of all hosts on
the network. With an --addn-hosts file, each dnsmasq instance is aware of all
the hosts on the network even if they do not give the lease for a host,
therefore each dnsmasq instance can resolve any host on their network even if
they did not provide the lease for it themselves.

Change-Id: Ic6d4f7854d250889dded5491e4693fcdce32ed00
Fixes: bug #1242712
Merge "Make dnsmasq aware of all names"
Merge "Prevent cross plugging router ports from other tenants"