Spice tests update.

Multiple minor and major changes in spice tests and configuration files:

- Move all *.cfg tests file into one spice.cfg file used for generating subtests.cfg to be able to influence order of spice tests since we like to run tests in particular sequences.
- Refactoring the base tests-spice.cfg to clean up the redundancies also and split up the tests per platform to be tested on.
- Modify kickstart to start X and gnome session right away after booting (and get rid of using startx in tests).
- Use different non-root user for Spice tests (since It's not recommended to use root as Desktop user).
- Add some authentications tests for remote-viewer client (with some negative scenarios).
- Add a new customized shutdown test which shuts both VMs used by spice tests and uses root ssh session (since we use non-root by default).
- Add a tests which verifies after shutdown that: Verify:
  1. guest is shutdown
  2. rv_connection is no longer established
  3. remote-viewer process is no longer running on the client.
- Minor changes based on runs

Tested on F18 and RHEL6.