tests/avocado/boot_xen.py: use class attribute

Rather than defining a single use variable, let's just use the class
attribute directly.

Signed-off-by: Cleber Rosa <crosa@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20231208190911.102879-11-crosa@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
diff --git a/tests/avocado/boot_xen.py b/tests/avocado/boot_xen.py
index f4b63c1..f29bc58 100644
--- a/tests/avocado/boot_xen.py
+++ b/tests/avocado/boot_xen.py
@@ -50,11 +50,10 @@ def launch_xen(self, xen_path):
 
         self.vm.set_console()
 
-        xen_command_line = self.XEN_COMMON_COMMAND_LINE
         self.vm.add_args('-machine', 'virtualization=on',
                          '-m', '768',
                          '-kernel', xen_path,
-                         '-append', xen_command_line,
+                         '-append', self.XEN_COMMON_COMMAND_LINE,
                          '-device',
                          'guest-loader,addr=0x47000000,kernel=%s,bootargs=console=hvc0'
                          % (kernel_path))