Metaclass Python 3.x Compatibility

According to the OpenStack style guide
(http://docs.openstack.org/developer/hacking/),
for Python 3.x compatibility use "six.add_metaclass"
instead of " __metaclass__."

Closes-Bug: #1236648
Change-Id: I2f507a90ee08cc05bd764549002a4656c187b6fc
Do not defer IPTables apply in firewall path

By default, iptables apply is deferred in L3 agent. For
external gateways, iptables is applied immediately (to
enable NAT for floating IP). Similarly, when firewall
is created/updated/deleted, iptable rules are applies
immediately.

Change-Id: I4f652a030ae23a71a2e20af2e8ef0ad5b882b80e
Closes-Bug: #1320775
NSX: get rid of the last Nicira/NVP bits

These were kept for bw compatibility in Icehouse, but
these are removed in Juno.

The king is dead, long live the king!

DocImpact
Blueprint: nicira-plugin-renaming

Change-Id: I49d19fec90ba191ed5b895fac8a884070f52119e
Merge "Do not defer IPTables apply in firewall path"
Merge "NSX: get rid of the last Nicira/NVP bits"
Merge "Metaclass Python 3.x Compatibility"