ml2 nexus fix vpc-pool config

[Carol Bouchard]

Initially vpc-pool config was going to be temporary. I wasn't coded correctly.
vpc-pool 1001,1025 generates Configures 1001 thru 1025 vpc entries in the data base
The config instead should have read:
vpc-pool 1001-1025

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/492176
Committed: https://git.openstack.org/cgit/openstack/networking-cisco/commit/?id=1fd2b3e7ae1fa399cf902bb389a1bbce30466fc2
Submitter: Jenkins
Branch: master

commit 1fd2b3e7ae1fa399cf902bb389a1bbce30466fc2
Author: Carol Bouchard <email address hidden>
Date: Wed Aug 9 11:26:48 2017 -0400

    Fix ML2 Nexus vpc_pool user config parameter

    The user config 'vpc_pool' was originally planned as a temp config
    but have decided to make it long-term. This changeset updates this
    config param to be consistent with other configs where range values
    are separated by '-' instead of a ',' and you can have any number
    of ranges and single values separated by ',' which was not
    previously handled since it was temp config.

    Additionally this changeset gets existing VPCs in the data base and
    compares against the user's vpc_pool config. This allows the user
    to add/remove to the existing pool which requires neutron restart.
    New configured entries not found in the data base will be added.
    Inactive entries in the data base not found in the user's configured
    list will be removed.

    Change-Id: I7e041c77461a95f655e6f38a70e3b9da357ac90b
    Closes-bug: #1707286