Update horizon local settings conf files for Juno

* Update local_settings
  - Add in description comments
  - Add new sections
* Update specs as needed
* Change metadata for apache2 to < 2.0.0 since it's not
backward compatible with 1.9.x.

Change-Id: I455624f809ad5968a9fbef3054c1bd10bcac5378
Closes-Bug: #1352956
Merge "Update horizon local settings conf files for Juno"