selftests: mark some tests as time sensitive

As it has already been done to some other tests, two other tests have
been producing false positives.  This has been observed recently in
package builds in build farms.

Let's run them only when `make check-full` is called, which is
usually done at dedicated machines with plenty of resources.

Reference: https://kojipkgs.fedoraproject.org/work/tasks/9189/19059189/build.log
Reference: https://kojipkgs.fedoraproject.org/work/tasks/9445/19069445/build.logSigned-off-by: NCleber Rosa <crosa@redhat.com>

selftests/functional/test_basic.py

@@ -646,6 +646,9 @@ class RunnerSimpleTest(unittest.TestCase):
                          "Avocado did not return rc %d:\n%s" %
                          (expected_rc, result))
 
+    @unittest.skipIf(os.environ.get("AVOCADO_CHECK_FULL") != "1",
+                     "Skipping test that take a long time to run, are "
+                     "resource intensive or time sensitve")
     def test_runner_onehundred_fail_timing(self):
         """
         We can be pretty sure that a failtest should return immediately. Let's

selftests/functional/test_loader.py

@@ -215,6 +215,9 @@ class LoaderTestFunctional(unittest.TestCase):
     def test_load_not_a_test_not_exec(self):
         self._test('notatest.py', NOT_A_TEST, 'NOT_A_TEST')
 
+    @unittest.skipIf(os.environ.get("AVOCADO_CHECK_FULL") != "1",
+                     "Skipping test that take a long time to run, are "
+                     "resource intensive or time sensitve")
     def test_runner_simple_python_like_multiple_files(self):
         mylib = script.TemporaryScript(
             'test2.py',