qmp: generalize watchdog-set-action to -no-reboot/-no-shutdown

Add a QMP command to allow for the behaviors specified by the
-no-reboot and -no-shutdown command line option to be set at runtime.
The new command is named set-action and takes optional arguments, named
after an event, that provide a corresponding action to take.

Example:

-> { "execute": "set-action",
     "arguments": {
	"reboot": "none",
	"shutdown": "poweroff",
	"watchdog": "debug" } }
<- { "return": {} }

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>
Message-Id: <1607705564-26264-4-git-send-email-alejandro.j.jimenez@oracle.com>
[Split the series differently, with -action based on the QMP command. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

monitor/qmp-cmds.c

@@ -26,6 +26,7 @@
 #include "ui/vnc.h"
 #include "sysemu/kvm.h"
 #include "sysemu/runstate.h"
+#include "sysemu/runstate-action.h"
 #include "sysemu/arch_init.h"
 #include "sysemu/blockdev.h"
 #include "sysemu/block-backend.h"
@@ -72,7 +73,7 @@ UuidInfo *qmp_query_uuid(Error **errp)
 
 void qmp_quit(Error **errp)
 {
-    no_shutdown = 0;
+    shutdown_action = SHUTDOWN_ACTION_POWEROFF;
     qemu_system_shutdown_request(SHUTDOWN_CAUSE_HOST_QMP_QUIT);
 }