selftests: Merge non-existing and ordered checks

The selftests.functional.test_basic.PluginsTest.test_plugin_order
executes the tests 3 times, for the last time only to check it does not
reports failure. Let's just add this missing plugin into the previous
check. If error occurs, one can always check manually which issue is
that (compare to thousands of executions where it goes well).
Signed-off-by: NLukáš Doktor <ldoktor@redhat.com>

selftests/functional/test_basic.py

@@ -969,7 +969,8 @@ class PluginsTest(AbsPluginsTest, unittest.TestCase):
             os.unlink(archives[0])
 
         config_content_zip_last = ("[plugins.result]\norder=['html', 'json',"
-                                   "'xunit', 'zip_archive']")
+                                   "'xunit', 'non_existing_plugin_is_ignored'"
+                                   ",'zip_archive']")
         config_zip_last = script.TemporaryScript("zip_last.conf",
                                                  config_content_zip_last)
         with config_zip_last:
@@ -981,14 +982,6 @@ class PluginsTest(AbsPluginsTest, unittest.TestCase):
             for result_output in result_outputs:
                 self.assertIn(result_output, zip_file_list)
 
-        config_content_missing = ("[plugins.result]\norder=['foo', "
-                                  "'html', 'json', 'xunit', "
-                                  "'zip_archive', 'bar']")
-        config_missing = script.TemporaryScript("missing.conf",
-                                                config_content_missing)
-        with config_missing:
-            run_config(config_missing)
-
     def test_Namespace_object_has_no_attribute(self):
         os.chdir(basedir)
         cmd_line = './scripts/avocado plugins'