OS-535/536 Fix flake8 issues and remove unused APIs

This fixes flake8 issues introduced by OS-532.
Includes unused method cleanup from base.py and neutron_ipam.py.

Change-Id: I8e19391a62d7848f93b43fe37a3b8a912ef97f8e
OS-500/OS-511 Remove os_instance_id EA when VM is deleted

Change-Id: I780f34352586d7ead97c9f704a86df75c0018a79
Fix merge issues and floating IP

This patch is intended to fix issues introduced by merge from other bp/*
branches:
 - flake8;
 - base.IPAMManager.allocate_ip() being removed;
 - broken floating IP functionality:
   dns_controller.disassociate_floatingip was never defined.

Change-Id: Iee9d262c600b9181bc9a0edc5dd4bab5074c1354
Merge pull request #9 from roman-verchikov/bp/infoblox-plugin-neutron

Fix merge issues