[1715] Test the unset command

It's shocking how much is not tested here. No surprise the missing
command was not discovered. Still, not adding tests for the others,
they'd probably fail and it would make the ticket a lot bigger.

src/bin/bindctl/tests/bindctl_test.py

@@ -365,10 +365,20 @@ class TestConfigCommands(unittest.TestCase):
         self.assertEqual((5, MultiConfigData.LOCAL),
                          self.tool.config_data.get_value("/foo/an_int"))
 
+        cmd = cmdparse.BindCmdParse("config unset identifier=\"foo/an_int\"")
+        self.tool.apply_config_cmd(cmd)
+
+        self.assertEqual((1, MultiConfigData.DEFAULT),
+                         self.tool.config_data.get_value("/foo/an_int"))
+
         # this should raise a NotFoundError
         cmd = cmdparse.BindCmdParse("config set identifier=\"foo/bar\" value=\"[]\"")
         self.assertRaises(isc.cc.data.DataNotFoundError, self.tool.apply_config_cmd, cmd)
 
+        cmd = cmdparse.BindCmdParse("config unset identifier=\"foo/bar\"")
+        self.assertRaises(isc.cc.data.DataNotFoundError,
+                          self.tool.apply_config_cmd, cmd)
+
         # this should raise a TypeError
         cmd = cmdparse.BindCmdParse("config set identifier=\"foo/an_int\" value=\"[]\"")
         self.assertRaises(isc.cc.data.DataTypeError, self.tool.apply_config_cmd, cmd)