qemu: Introduce nbd-server-stop command

This will be used after all migration work is done
to stop NBD server running on destination.  It
doesn't take any arguments, just issues a command.

src/qemu/qemu_monitor.c

@@ -3507,3 +3507,22 @@ int qemuMonitorNBDServerAdd(qemuMonitorPtr mon,
 
     return qemuMonitorJSONNBDServerAdd(mon, deviceID, writable);
 }
+
+int qemuMonitorNBDServerStop(qemuMonitorPtr mon)
+{
+    VIR_DEBUG("mon=%p", mon);
+
+    if (!mon) {
+        virReportError(VIR_ERR_INVALID_ARG, "%s",
+                       _("monitor must not be NULL"));
+        return -1;
+    }
+
+    if (!mon->json) {
+        virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
+                       _("JSON monitor is required"));
+        return -1;
+    }
+
+    return qemuMonitorJSONNBDServerStop(mon);
+}

src/qemu/qemu_monitor.h

@@ -682,6 +682,7 @@ int qemuMonitorNBDServerStart(qemuMonitorPtr mon,
 int qemuMonitorNBDServerAdd(qemuMonitorPtr mon,
                             const char *deviceID,
                             bool writable);
+int qemuMonitorNBDServerStop(qemuMonitorPtr);
 /**
  * When running two dd process and using <> redirection, we need a
  * shell that will not truncate files.  These two strings serve that

src/qemu/qemu_monitor_json.c

@@ -4688,3 +4688,24 @@ qemuMonitorJSONNBDServerAdd(qemuMonitorPtr mon,
     virJSONValueFree(reply);
     return ret;
 }
+
+int
+qemuMonitorJSONNBDServerStop(qemuMonitorPtr mon)
+{
+    int ret = -1;
+    virJSONValuePtr cmd;
+    virJSONValuePtr reply = NULL;
+
+    if (!(cmd = qemuMonitorJSONMakeCommand("nbd-server-stop",
+                                           NULL)))
+        return ret;
+
+    ret = qemuMonitorJSONCommand(mon, cmd, &reply);
+
+    if (ret == 0)
+        ret = qemuMonitorJSONCheckError(cmd, reply);
+
+    virJSONValueFree(cmd);
+    virJSONValueFree(reply);
+    return ret;
+}

src/qemu/qemu_monitor_json.h

@@ -340,4 +340,5 @@ int qemuMonitorJSONNBDServerStart(qemuMonitorPtr mon,
 int qemuMonitorJSONNBDServerAdd(qemuMonitorPtr mon,
                                 const char *deviceID,
                                 bool writable);
+int qemuMonitorJSONNBDServerStop(qemuMonitorPtr mon);
 #endif /* QEMU_MONITOR_JSON_H */