ctrl_test_runner.py: use proper constant as test db path

Change-Id: I9533a9ff8c0f8d24c678583a9197143a187908f3
diff --git a/tests/ctrl_test_runner.py b/tests/ctrl_test_runner.py
index 7c14f50..1c5ec2a 100644
--- a/tests/ctrl_test_runner.py
+++ b/tests/ctrl_test_runner.py
@@ -178,7 +178,7 @@
 
     def tearDown(self):
         super(TestCtrlHLR, self).tearDown()
-        os.unlink("hlr_ctrl_test.db")
+        os.unlink(self.HLR_DB)
 
     def ctrl_command(self):
         return ["./src/osmo-hlr", "-c", "doc/examples/osmo-hlr.cfg", '-l', 'hlr_ctrl_test.db']