virt: Sync serial console output log behavior

* libvirt automatically creates an alias for serial devices
  starting with 'serial0'.  However, base.cfg defaults to
  counting from serial1.  By changing it to serial0, console
  logfile names from qemu-kvm and libvirt subtests will match.

* libvirt VM class should log serial_console output to same
  place as qemu-kvm.  Added methods to help set this up
  and help with cleanup in key places.

* Updated unattended_install test to use the same completion
  file for both qemu-kvm and libvirt - since both now log
  to uniform filenames.

* Set default machine_type=pc by hard-coding filter on
  i440fx variant (from machines.cfg).

* Change fedora 18 & 19 configs to reference media by label.

* Update .gitignore to ignore codespell and github tools cache.

* Add os_variant parameters to Fedora/RHEL/OpenSUSE/Ubuntu/SLES

Signed-off-by: Chris Evich <cevich@redhat.com>