[2113] Avoid a warning

The warning would be provoked by checking a MasterFiles type data
source. The client list skips it, because cache is disabled, and it
complains it won't be able to serve. That is not a problem while
checking configuration, so the zones are stolen from it.

src/bin/cfgmgr/plugins/datasrc_config_plugin.py

@@ -20,6 +20,7 @@ import isc.dns
 import isc.datasrc
 import json
 import os.path
+import copy
 
 spec = module_spec_from_file(path_search('datasrc.spec', PLUGIN_PATHS))
 
@@ -44,11 +45,10 @@ def check(config):
             return "The class '" + rr_class_str + "' is invalid"
 
         dlist = isc.datasrc.ConfigurableClientList(rr_class)
-        client_config = classes.get(rr_class_str)
+        # We get a copy here, as we are going to mangle the configuration.
-        try:
+        # But we don't want our changes to propagate outside, to the real
-            dlist.configure(json.dumps(client_config), False)
+        # configuration.
-        except isc.datasrc.Error as dse:
+        client_config = copy.deepcopy(classes.get(rr_class_str))
-            return str(dse)
 
         for client in client_config:
             if client['type'] == 'MasterFiles':
@@ -64,6 +64,16 @@ def check(config):
                         return str(e)
                     if not os.path.exists(params[name]):
                         return "Master file " + params[name] + " does not exist"
+                # We remove the list of zones locally. We already checked them,
+                # and the client list would have skipped them anyway, as we
+                # forbid cache. But it would produce a warning and we don't
+                # want that here.
+                client['params'] = {}
+
+        try:
+            dlist.configure(json.dumps(client_config), False)
+        except isc.datasrc.Error as dse:
+            return str(dse)
     return None
 
 def load():

src/bin/cfgmgr/plugins/tests/datasrc_test.py

@@ -16,26 +16,35 @@
 # Make sure we can load the module, put it into path
 import sys
 import os
+import unittest
+import json
 sys.path.extend(os.environ["B10_TEST_PLUGIN_DIR"].split(':'))
 import isc.log
 
 import datasrc_config_plugin
-import unittest
 
 class DatasrcTest(unittest.TestCase):
     def reject(self, config):
         """
         Just a shortcut to check the config is rejected.
         """
+        old = json.dumps(config)
         self.assertIsNotNone(datasrc_config_plugin.check({"classes":
                                                          config}))
+        # There's some data mangling inside the plugin. Check it does
+        # not propagate out, as it could change the real configuration.
+        self.assertEqual(old, json.dumps(config))
 
     def accept(self, config):
         """
         Just a shortcut to check the config is accepted.
         """
+        old = json.dumps(config)
         self.assertIsNone(datasrc_config_plugin.check({"classes":
                                                       config}))
+        # There's some data mangling inside the plugin. Check it does
+        # not propagate out, as it could change the real configuration.
+        self.assertEqual(old, json.dumps(config))
 
     def test_load(self):
         """