tests/acceptance/virtio-gpu.py: preserve virtio-user-gpu log

Preserve log at location already prepared for keeping the test's log
files.

While at it, log info about its location (in the main test log
file), instead of printing it out.

Reference: https://avocado-framework.readthedocs.io/en/85.0/api/test/avocado.html#avocado.Test.logdir


Signed-off-by: Cleber Rosa <crosa@redhat.com>
Reviewed-by: Wainer dos Santos Moschetta <wainersm@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
[philmd: use full sentence]
Message-Id: <20210211220146.2525771-7-crosa@redhat.com>

Signed-off-by: Cleber Rosa <crosa@redhat.com>

tests/acceptance/virtio-gpu.py

@@ -119,10 +119,11 @@ def test_vhost_user_vga_virgl(self):
         os.set_inheritable(vug_sock.fileno(), True)
 
         self._vug_log_path = os.path.join(
-            self.vm._test_dir, "vhost-user-gpu.log"
+            self.logdir, "vhost-user-gpu.log"
         )
         self._vug_log_file = open(self._vug_log_path, "wb")
-        print(self._vug_log_path)
+        self.log.info('Complete vhost-user-gpu.log file can be '
+                      'found at %s', self._vug_log_path)
 
         vugp = subprocess.Popen(
             [vug, "--virgl", "--fd=%d" % vug_sock.fileno()],