SimpleTest: with the implementation of filename, basedir is unnecessary

The implementation of basedir from Avocado Test is also sufficient for
SimpleTest now that the `filename` property is implemented.
Signed-off-by: NCleber Rosa <crosa@redhat.com>

avocado/core/test.py

@@ -585,13 +585,6 @@ class SimpleTest(Test):
                                          base_logdir=base_logdir, tag=tag, job=job)
         self.path = name
 
-    @property
-    def datadir(self):
-        """
-        Returns the path to the directory that contains test data files
-        """
-        return self.name + '.data'
-
     @property
     def filename(self):
         """