OpenStack release numbers should not be hard-coded

[Jill Rouleau]

OpenStack major.minor release numbers are hard-coded in contrib/openstack/utils.py. This results in charm errors anytime an update is released, such as in this neutron-api case:
juju-log FATAL ERROR: Could not determine OpenStack codename for version 7.1

Requiring:

    'neutron-common': OrderedDict([
        ('7.0', 'liberty'),
+ ('7.1', 'liberty'),
        ('8.0', 'mitaka'),
        ('8.1', 'mitaka'),

This causes many production problems as unplanned charm upgrades (or on-unit hacks) must be made to allow hooks to fire.

[Nobuto Murata (nobuto)]

FWIW, it would be fixed already. Charm helpers has been changed to match major versions only (7.* in this case).
http://bazaar.launchpad.net/~charm-helpers/charm-helpers/devel/revision/576

Also, neutron-api charm should already have the commit as:
$ git branch --contains 258b7196e8211c4172094c87f5486b700260b835
* master
  stable/16.07

$ git show -s 258b7196e8211c4172094c87f5486b700260b835
commit 258b7196e8211c4172094c87f5486b700260b835
Author: James Page <email address hidden>
Date: Fri May 27 11:14:05 2016 +0100

    Resync charm helpers

    Add support for OpenStack Newton and Ocata.

    Rework version detection code to just match on major version for
    OpenStack projects using semantic versioning.

    Provide fallback version detection based on major.minor versions
    for swift packages.

    Rework config-flags support helpers.

    Fix is_ip function to correctly detect both IPv4 and IPv6 addresses.

    Change-Id: I52dcf27d1028057492b7db6e63ff3ada87b726da