qtest/migration-test.c: Add tests with compress enabled There has never been tests for migration with compress enabled. Add suitable tests, testing with compress-wait-thread = false too. Signed-off-by: Lukas Straub <lukasstraub2@web.de> Acked-by: Peter Xu <peterx@redhat.com> Reviewed-by: Juan Quintela <quintela@redhat.com> Signed-off-by: Juan Quintela <quintela@redhat.com>