REMOVEME: testing qemu.tests.qdev_example_test

This is example test for hotplug purposes.

Currently it has 4 variants = 4 phases:
1) env_process creates one standard VM and in test it hotplugs
   a stg disk (disk params are taken from params)
2) this test needs VM with stg disk. Env_process compares old
   VM with new params and discovers, that old VM already has
   stg disk and they matches, so it continue executing the test.
3) This test also uses additional disk, but the id doesn't match.
   env_process recreates the VM.
4) In this test env_process also recreates VM as the filenames of
   the additional disk doesn't match.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>