tests/avocado/replay_kernel: Mark the test_x86_64_pc as flaky

It's failing very often, so don't run this by default anymore
until it gets fixed.

Message-ID: <20231114153019.295131-1-thuth@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>

tests/avocado/replay_kernel.py

@@ -81,7 +81,8 @@ def run_rr(self, kernel_path, kernel_command_line, console_pattern,
         logger.info('replay overhead {:.2%}'.format(t2 / t1 - 1))
 
 class ReplayKernelNormal(ReplayKernelBase):
-    @skipIf(os.getenv('GITLAB_CI'), 'Running on GitLab')
+
+    @skipUnless(os.getenv('QEMU_TEST_FLAKY_TESTS'), 'Test sometimes gets stuck')
     def test_x86_64_pc(self):
         """
         :avocado: tags=arch:x86_64