pytest: add an example test fetching test directory and ATF vars.

MFC after:	2 weeks

tests/examples/test_examples.py

@@ -49,6 +49,16 @@ def test_one(self):
     def test_two(self):
         pass
 
+    @pytest.mark.skip(reason="comment me to run the test")
+    def test_get_properties(self, request):
+        """Shows fetching of test src dir and ATF-set variables"""
+        print()
+        print("SRC_DIR={}".format(request.fspath.dirname))
+        print("ATF VARS:")
+        for k, v in self.atf_vars.items():
+            print("  {}: {}".format(k, v))
+        print()
+
     @pytest.mark.skip(reason="comment me to run the test")
     @pytest.mark.require_user("unprivileged")
     def test_syscall_failure(self):