qemu: Add qemu_no_shutdown test case.

fix bugs:
RFE: '-no-shutdown' flag should keep working

Signed-off-by: Yunping Zheng <yunzheng@redhat.com>
Acked-by: Feng Yang <fyang@redhat.com>
Signed-off-by: Feng Yang <fyang@redhat.com>
qemu.tests.qemu_no_shutdow: Update it to catch more qemu bug and script bug fix

Change enable_no_shutdown to disable_shutdown.
Delete time.sleep(interval).
Check VM is alive before vm pid check.
Add virt_test_type in config
Signed-off-by: Feng Yang <fyang@redhat.com>