Update horizon's local_settings.py template for Juno

This change brings in some of the differences in Juno's
local_settings.py file and removes FLAVOR_EXTRA_KEYS since that is now
deprecated.

Some opinion has been applied to supported_provider_types by removing
the ability to create local and gre networks via horizon.  This can be
adjusted if anyone believes these should be added (or others removed).
Fix mariadb & galera install order

* We were installing mariadb/galera as part of the galera play to ensure
  we could control the startup and preseed.
* This changes the play back to do this properly, instead of installing
  it as part of the "common" play.
* This leaves the packages to be installed in the common repo_packages
  file

Fixes-Bug: #222
Merge pull request #224 from andymcc/galera_fix

Fix mariadb & galera install order
removed openstack common play as its no longer used
Merge pull request #225 from cloudnull/removed-openstack-common

Removed openstack common play as its no longer used
Merge pull request #223 from mattt416/trello_35

Update horizon's local_settings.py template for Juno
Install Tempest in utility container

* Tempest playbook added to openstack dir
* glance_image module added for creating images and gathering image
  facts
* tempest_resources role added to create tempest prerequisites (cirros
  image, tenants)
* tempest role added for configuring tempest
* rpc_tempest_gate.sh added to /root in utility containers
Merge pull request #227 from hughsaunders/utility_tempest

Install Tempest in utility container