Journal plugin: only attempt to close it if it has been initialized

Attempting to close a journal that wasn't initialized is certainly a
bug.  This will check for its initialization first.
Signed-off-by: NCleber Rosa <crosa@redhat.com>

avocado/plugins/journal.py

@@ -70,7 +70,8 @@ class JournalResult(ResultEvents):
             self.journal_initialized = True
 
     def _shutdown_journal(self):
-        self.journal.close()
+        if self.journal_initialized:
+            self.journal.close()
 
     def _record_job_info(self, state):
         res = self.journal_cursor.execute("SELECT unique_id FROM job_info")

selftests/functional/test_output.py

@@ -479,6 +479,9 @@ class OutputPluginTest(unittest.TestCase):
         self.assertNotIn("RESULTS    : PASS ", result.stdout)
         self.assertNotIn("JOB TIME   :", result.stdout)
 
+        # Check that plugins do not produce errors
+        self.assertNotIn("Error running method ", result.stderr)
+
     def tearDown(self):
         shutil.rmtree(self.tmpdir)