The changes were based on the latest commits on the monasca-api
repository until the commit 5f37594fe705b909507a82cd2ef03c2f972fcca0
on 15-Jul-2016.

Also, added a task to drop required plugin configs on the
/root directory.

    - Added configuration for the monasca-agent/monasca-user users;
    - Added variable for specifying the horizon directory;
    - Deleted tasks for removing plugins causing error, ignore
      erros instead.