Remove unused variable

o neutron/services/firewall/drivers/linux/iptables_fwaas.py:FWAAS_CHAIN
  = 'fwaas'

  This variable was added in the following commit.

    commit 7e487160867d2c2059d556d0d3af50bc8e8838fa
    Author: Rajesh Mohan <rajesh.mlists@gmail.com>
    Date:   Fri Jun 21 17:55:08 2013 -0700

        Firewall as a Service (FWaaS) Iptables Driver

  But there is no evidence that was used.

Change-Id: I5633e74e2441b71e3dddaa0c2f6a5804778e21e1
Fix H302 violations in extensions package

H302 violation is reported by flake8 when importing separated objects from
modules instead of importing the whole module.
e.g.   from package.module import function
       function()
is changed to
       from package import module
       module.function()

Change-Id: I570eeee2a7633c1590b54ac98b411a71fc9d4f4e
Partial-Bug: #1291032
Merge "Fix H302 violations in extensions package"
Merge "Remove unused variable"