latest job result: create the `latest` symlink at the job beginning

Instead of creating at the end of the job. This allows users running
long (time wise) jobs to be monitored by "following" the
$AVOCADO_RESULT/latest/job.log file.

This implements the card described at:

 https://trello.com/c/QJ4wCD8x/447-reconsider-when-the-latest-log-symlink-is-createdSigned-off-by: NCleber Rosa <crosa@redhat.com>

avocado/core/job.py

@@ -443,6 +443,8 @@ class Job(object):
         self.args.test_result_total = mux.get_number_of_tests(test_suite)
 
         self._make_test_result()
+        if not self.standalone:
+            self._update_latest_link()
         self._make_test_runner()
         self._start_sysinfo()
 
@@ -452,8 +454,6 @@ class Job(object):
         failures = self.test_runner.run_suite(test_suite, mux,
                                               timeout=self.timeout)
         self.view.stop_file_logging()
-        if not self.standalone:
-            self._update_latest_link()
         # If it's all good so far, set job status to 'PASS'
         if self.status == 'RUNNING':
             self.status = 'PASS'

selftests/all/functional/avocado/basic_tests.py

@@ -237,6 +237,24 @@ class RunnerOperationTest(unittest.TestCase):
                                                                 result))
         self.assertIn('"status": "ERROR"', result.stdout)
 
+    def test_early_latest_result(self):
+        """
+        Tests that the `latest` link to the latest job results is created early
+        """
+        os.chdir(basedir)
+        cmd_line = ('./scripts/avocado run --sysinfo=off --job-results-dir %s examples/tests/sleeptest.py '
+                    '-m examples/tests/sleeptest.py.data/sleeptest.yaml' % self.tmpdir)
+        avocado_process = process.SubProcess(cmd_line)
+        avocado_process.start()
+        link = os.path.join(self.tmpdir, 'latest')
+        for trial in xrange(0, 50):
+            time.sleep(0.1)
+            if os.path.exists(link) and os.path.islink(link):
+                avocado_process.terminate()
+                break
+        self.assertTrue(os.path.exists(link))
+        self.assertTrue(os.path.islink(link))
+
     def tearDown(self):
         shutil.rmtree(self.tmpdir)