JUnit XML output: Include timezone information in XML

JUnit writes local-time without a timezone by default.  This means that
JUnit XML parsers default to local-time.  The portal doesn't know what
timezone the user of stbt-rig wants so these timestamps can be interpreted
incorrectly.  This change includes timezone information in the XML output.

There is a small chance of incompatibilty caused by this change.  If you
experience this please get in contact at support@stb-tester.com.

stbt_rig.py

@@ -839,7 +839,8 @@ def list_results(self):
 
     def list_results_xml(self):
         r = self.portal._get(
-            '/api/v2/results.xml', params={'filter': 'job:%s' % self.job_uid})
+            '/api/v2/results.xml', params={'filter': 'job:%s' % self.job_uid,
+                                           'include_tz': 'true'})
         r.raise_for_status()
         return r.text
 

test_stbt_rig.py

@@ -208,6 +208,7 @@ def get_results():
         @self.app.route('/api/v2/results.xml')
         def get_results_xml():
             assert flask.request.args['filter'] == 'job:/mynode/6Pfq/167'
+            assert flask.request.args['include_tz'] == 'true'
             return PortalMock.RESULTS_XML
 
         @self.app.route('/api/v2/results/<path:result_id>')
@@ -276,7 +277,7 @@ def on_run_tests(self, j):
     RESULTS_XML = (
         '<testsuite disabled="0" errors="0" failures="0" '
         'name="test" skipped="0" tests="1" time="3.270815" '
-        'timestamp="2019-06-12T15:26:35">'
+        'timestamp="2019-06-12T15:26:35+00:00">'
         '<testcase classname="tests/test.py" name="test_my_tests" '
         'time="3.270815"/>'
         '</testsuite>')