Fix package dependency installation.

 * The previous list of os packages was insufficient to support
   installation of all of tempest's python dependencies.  This
   change adds the necessary dependencies for redhat.  I leave it
   as an exercise for a non-redhat employee to update the
   corresponding list for debian.
 * stdlib's ensure_packages method is used instead of per-package
   checks for definition.
 * easy_install is used to install pip, rather than installing pip
   from a package and having both packaged and unpackaged veresions
   of pip installed on the host.

Change-Id: Ie4f02d04f6a769c0fffb13d9c16dc3a3d4d533c1
Switch to ini_setting for managing tempest.conf.

 * The previous way of customizing tempest.conf was problematic
   for a number of reasons:

   - default values were being defined in the manifest and those
     values differed from the defaults in tempest.conf.sample.
     Defaults should be the province of the tempest maintainers,
     not the puppet module.
   - the use of templating meant that extra work would have to be
     expended maintaining the templates, not only for releases
     but also for the upstream master.

 * This changeset switches to using ini_setting to ensure that:

   - individual configuration settings can be set ad hoc, and
     the upstream defaults will be left alone if no value is provided.
   - tempest.conf can be sourced from the tempest repo sample rather
     than having to be maintained in the module.

 * Other included fixes:

   - removing unused glance uri configuration
   - consolidating the identity uri parameters into a single parameter,
     since that is how it is represented in tempest.conf

Change-Id: Idcdf7a1002a447b7d3ae909ca9043b8d7143c313