Job: prepare for the removal of old style result plugins

This change combines the activation of all old style result plugins
into a single method.  It also names it accordingly, so it's easier
to spot it when it's finally removed.

Another reason for this change is that the old docstring was outdated
and inaccurate.
Signed-off-by: NCleber Rosa <crosa@redhat.com>

avocado/core/job.py

@@ -251,32 +251,33 @@ class Job(object):
         self.test_runner = test_runner_class(job=self,
                                              test_result=self.result_proxy)
 
-    def _set_output_plugins(self):
-        if getattr(self.args, 'test_result_classes', None) is not None:
-            for klass in self.args.test_result_classes:
-                test_result_instance = klass(self)
-                self.result_proxy.add_output_plugin(test_result_instance)
-        else:
-            self.result_proxy.add_output_plugin(result.Result(self))
-
-    def _make_test_result(self):
+    def _make_old_style_test_result(self):
         """
-        Set up output plugins.
+        Old style result output plugins setup.
 
-        The basic idea behind the output plugins is:
+        This supports the activation of old style result classes which are
+        registered with :func:`avocado.core.result.register_test_result_class`.
 
-        * If there are any active output plugins, use them
-        * If at the end we only have 2 output plugins (Xunit and JSON), we can
-          add the human output plugin.
+        Then, if no plugin has claimed the STDOUT, activate a HumanResult
+        instance.
+
+        Finally, if no old style result plugin is given, activate a bare
+        bones Result instance, as they serve result information (only)
+        to the new style result plugins.
         """
         if self.args:
-            # If there are any active output plugins, let's use them
-            self._set_output_plugins()
+            if getattr(self.args, 'test_result_classes', None) is not None:
+                for klass in self.args.test_result_classes:
+                    test_result_instance = klass(self)
+                    self.result_proxy.add_output_plugin(test_result_instance)
 
         if not getattr(self.args, 'stdout_claimed_by', False) or self.standalone:
             human_plugin = result.HumanResult(self)
             self.result_proxy.add_output_plugin(human_plugin)
 
+        if not self.result_proxy.output_plugins:
+            self.result_proxy.add_output_plugin(result.Result(self))
+
     def _make_test_suite(self, urls=None):
         """
         Prepares a test suite to be used for running tests
@@ -457,7 +458,7 @@ class Job(object):
                                                        "%s" % details)
         self.args.test_result_total = mux.get_number_of_tests(self.test_suite)
 
-        self._make_test_result()
+        self._make_old_style_test_result()
         if not (self.standalone or getattr(self.args, "dry_run", False)):
             self._update_latest_link()
         self._make_test_runner()