Test: remove reference related methods from public namespace

The methods `record_reference_stdout`, `record_reference_stderr`
`check_reference_stdout` and `check_reference_stderr` are publicly
visible, but are not intended to be used by test writers and are
not intended to have API stability.

Let's rename them so that they're hidden from the Avocado test
writer.
Signed-off-by: NCleber Rosa <crosa@redhat.com>

avocado/core/test.py

@@ -315,15 +315,15 @@ class Test(unittest.TestCase):
         """
         pass
 
-    def record_reference_stdout(self):
+    def _record_reference_stdout(self):
         utils_path.init_dir(self.datadir)
         shutil.copyfile(self.stdout_file, self.expected_stdout_file)
 
-    def record_reference_stderr(self):
+    def _record_reference_stderr(self):
         utils_path.init_dir(self.datadir)
         shutil.copyfile(self.stderr_file, self.expected_stderr_file)
 
-    def check_reference_stdout(self):
+    def _check_reference_stdout(self):
         if os.path.isfile(self.expected_stdout_file):
             expected = genio.read_file(self.expected_stdout_file)
             actual = genio.read_file(self.stdout_file)
@@ -331,7 +331,7 @@ class Test(unittest.TestCase):
                    'Actual:\n%s\nExpected:\n%s' % (actual, expected))
             self.assertEqual(expected, actual, msg)
 
-    def check_reference_stderr(self):
+    def _check_reference_stderr(self):
         if os.path.isfile(self.expected_stderr_file):
             expected = genio.read_file(self.expected_stderr_file)
             actual = genio.read_file(self.stderr_file)
@@ -405,22 +405,22 @@ class Test(unittest.TestCase):
             if job_standalone or no_record_mode:
                 if not disable_output_check:
                     try:
-                        self.check_reference_stdout()
+                        self._check_reference_stdout()
                     except Exception, details:
                         stacktrace.log_exc_info(sys.exc_info(),
                                                 logger='avocado.test')
                         stdout_check_exception = details
                     try:
-                        self.check_reference_stderr()
+                        self._check_reference_stderr()
                     except Exception, details:
                         stacktrace.log_exc_info(sys.exc_info(),
                                                 logger='avocado.test')
                         stderr_check_exception = details
             elif not job_standalone:
                 if output_check_record in ['all', 'stdout']:
-                    self.record_reference_stdout()
+                    self._record_reference_stdout()
                 if output_check_record in ['all', 'stderr']:
-                    self.record_reference_stderr()
+                    self._record_reference_stderr()
 
         # pylint: disable=E0702
         if test_exception is not None: