python/machine.py: upgrade vm.cmd() method

The method is not popular in iotests, we prefer use vm.qmp() and then
check success by hand. But that's not optimal. To simplify movement to
vm.cmd() let's support same interface improvements like in vm.qmp().

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 20231006154125.1068348-7-vsementsov@yandex-team.ru
Signed-off-by: John Snow <jsnow@redhat.com>

python/qemu/machine/machine.py

@@ -708,13 +708,23 @@ def qmp(self, cmd: str,
         return ret
 
     def cmd(self, cmd: str,
-            conv_keys: bool = True,
+            args_dict: Optional[Dict[str, object]] = None,
+            conv_keys: Optional[bool] = None,
             **args: Any) -> QMPReturnValue:
         """
         Invoke a QMP command.
         On success return the response dict.
         On failure raise an exception.
         """
+        if args_dict is not None:
+            assert not args
+            assert conv_keys is None
+            args = args_dict
+            conv_keys = False
+
+        if conv_keys is None:
+            conv_keys = True
+
         qmp_args = self._qmp_args(conv_keys, args)
         ret = self._qmp.cmd(cmd, **qmp_args)
         if cmd == 'quit':