selftests/unit/test_xunit.py: junit XSD file is only used in one test

So it makes no sense to use in the setup phase.  Let's move that
closer to its actual usage.
Signed-off-by: NCleber Rosa <crosa@redhat.com>

selftests/unit/test_xunit.py

@@ -52,9 +52,6 @@ class xUnitSucceedTest(unittest.TestCase):
         self.test1 = SimpleTest(job=self.job, base_logdir=self.tmpdir)
         self.test1._Test__status = 'PASS'
         self.test1.time_elapsed = 1.23
-        junit_xsd = os.path.join(os.path.dirname(__file__),
-                                 os.path.pardir, ".data", 'junit-4.xsd')
-        self.junit = os.path.abspath(junit_xsd)
 
     def tearDown(self):
         errs = []
@@ -87,12 +84,14 @@ class xUnitSucceedTest(unittest.TestCase):
         els = dom.getElementsByTagName('testcase')
         self.assertEqual(len(els), 1)
 
-        with open(self.junit, 'r') as f:
+        junit_xsd = os.path.abspath(os.path.join(os.path.dirname(__file__),
+                                                 os.path.pardir, ".data", 'junit-4.xsd'))
+        with open(junit_xsd, 'r') as f:
             xmlschema = etree.XMLSchema(etree.parse(f))   # pylint: disable=I1101
         # pylint: disable=I1101
         self.assertTrue(xmlschema.validate(etree.parse(BytesIO(xml))),
                         "Failed to validate against %s, content:\n%s\nerror log:\n%s" %
-                        (self.junit, xml, xmlschema.error_log))
+                        (junit_xsd, xml, xmlschema.error_log))
 
     def test_max_test_log_size(self):
         log = tempfile.NamedTemporaryFile(dir=self.tmpdir, delete=False)