Fix termination by signal with -no-shutdown

On signals such as SIGTERM qemu should exit instead of just stopping the VM
even with -no-shutdown.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

vl.c

@@ -1296,6 +1296,7 @@ void qemu_system_killed(int signal, pid_t pid)
 {
     shutdown_signal = signal;
     shutdown_pid = pid;
+    no_shutdown = 0;
     qemu_system_shutdown_request();
 }