Add enable_security_group to BigSwitch and OneConvergence ini files

It is a follow up patch for https://review.openstack.org/#/c/67281/.

Change-Id: I38463b3879ab2d7469a85ef00426b2b602fa825a
Closes-Bug: #1296000
Add script to migrate ovs or lb db to ml2 db

This script migrates an ovs or lb database to work with ml2.
The script's docstring provides details as to how it is intended to
work.

I've tested this manually on a trivial deployment, and would like
to add support for testing the migration with grenade.  However,
that will have to wait until grenade support for neutron has
merged.

DocImpact

Implements: blueprint ml2-deprecated-plugin-migration

Change-Id: I1eb908c866e19f72e61f687d56a0bc391cdb4760
Merge "Add script to migrate ovs or lb db to ml2 db"
Replace a usage of the deprecated root_helper option

This change replaces a usage of the deprecated root_helper option
by the usage of get_root_helper result.

Change-Id: Icfc698243784557cbf987a817c13d0b80969e5d3
Closes-Bug: #1297145
ML2 Cisco Nexus MD: Remove workaround for bug 1276395

Before bug 1276395 was merged the delete_port_postcommit() mechanism
drivers did not have access to the bound_segment information that was
in the process of being deleted.
Code was added to the cisco_nexus md to workaround this issue.
This code can now be removed.

Change-Id: If47ef1958bf4de863995b9cfc042abf5bc849e24
Closes-Bug: 1297321
Merge "Add enable_security_group to BigSwitch and OneConvergence ini files"
Merge "ML2 Cisco Nexus MD: Remove workaround for bug 1276395"
Merge "Replace a usage of the deprecated root_helper option"