Python libs: close console sockets before shutting down the VMs

Currently, the console socket on QEMUMachine is closed after the QMP
command to gracefully exit QEMU is executed.  Because of a possible
deadlock (QEMU waiting for the socket to become writable) let's close
the console socket earlier.

Reference: <20190607034214.GB22416@habkost.net>
Reference: https://bugs.launchpad.net/qemu/+bug/1829779
From: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Cleber Rosa <crosa@redhat.com>
Message-Id: <20190911023558.4880-2-crosa@redhat.com>

python/qemu/machine.py

@@ -277,10 +277,6 @@ def _post_shutdown(self):
 
         self._qemu_log_path = None
 
-        if self._console_socket is not None:
-            self._console_socket.close()
-            self._console_socket = None
-
         if self._temp_dir is not None:
             shutil.rmtree(self._temp_dir)
             self._temp_dir = None
@@ -342,6 +338,13 @@ def shutdown(self, has_quit=False):
         """
         Terminate the VM and clean up
         """
+        # If we keep the console socket open, we may deadlock waiting
+        # for QEMU to exit, while QEMU is waiting for the socket to
+        # become writeable.
+        if self._console_socket is not None:
+            self._console_socket.close()
+            self._console_socket = None
+
         if self.is_running():
             try:
                 if not has_quit: