Process vmstop requests in IO thread

A pending vmstop request is also a reason to leave the inner main loop.
So far we ignored it, and pending stop requests issued over VCPU threads
were simply ignored.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

vl.c

@@ -1391,15 +1391,11 @@ void main_loop_wait(int nonblocking)
 
 static int vm_can_run(void)
 {
-    if (powerdown_requested)
-        return 0;
-    if (reset_requested)
-        return 0;
-    if (shutdown_requested)
-        return 0;
-    if (debug_requested)
-        return 0;
-    return 1;
+    return !(powerdown_requested ||
+             reset_requested ||
+             shutdown_requested ||
+             debug_requested ||
+             vmstop_requested);
 }
 
 qemu_irq qemu_system_powerdown;