use the recommended yaml.safe_load function

reason: with pyyaml >= 5, the load function without Loader is deprecated.
Even if we do not use version 5 for now, we should use good practices.
https://pyyaml.org/wiki/PyYAMLDocumentation#loading-yaml
yaml/pyyaml#257

xivo_confgen/tests/test_dird.py

@@ -1,5 +1,5 @@
 # -*- coding: utf-8 -*-
-# Copyright 2015-2018 The Wazo Authors  (see the AUTHORS file)
+# Copyright 2015-2019 The Wazo Authors  (see the AUTHORS file)
 # SPDX-License-Identifier: GPL-3.0-or-later
 
 import unittest
@@ -38,7 +38,7 @@ def test_views_yml(self, _DisplayGenerator, _PhoneAssociationGenerator, _Associa
                               'profile_to_display': 'associations',
                               'profile_to_display_phone': 'phone_associations'}}
 
-        assert_that(yaml.load(result), equal_to(expected))
+        assert_that(yaml.safe_load(result), equal_to(expected))
 
 
 class TestNoContextSeparationDirdFrontendViewsGenerators(unittest.TestCase):
@@ -197,4 +197,4 @@ def test_services_yml(self):
                                  'favorites': 'favorites',
                                  'reverse': 'reverses'}}
 
-        assert_that(yaml.load(result), equal_to(expected))
+        assert_that(yaml.safe_load(result), equal_to(expected))

xivo_confgen/tests/test_dird_phoned.py

@@ -1,5 +1,5 @@
 # -*- coding: utf-8 -*-
-# Copyright (C) 2015 Avencall
+# Copyright 2015-2019 The Wazo Authors  (see the AUTHORS file)
 # SPDX-License-Identifier: GPL-3.0-or-later
 
 import unittest
@@ -27,4 +27,4 @@ def test_config_yml(self, mock_phone_access_dao):
             }
         }
 
-        assert_that(yaml.load(result), equal_to(expected))
+        assert_that(yaml.safe_load(result), equal_to(expected))

xivo_confgen/tests/test_xivo.py

@@ -1,5 +1,5 @@
 # -*- coding: utf-8 -*-
-# Copyright (C) 2015 Avencall
+# Copyright 2015-2019 The Wazo Authors  (see the AUTHORS file)
 # SPDX-License-Identifier: GPL-3.0-or-later
 
 import yaml
@@ -29,4 +29,4 @@ def test_uuid_yml(self):
             'uuid': 'sentinel-uuid',
         }
 
-        assert_that(yaml.load(result), equal_to(expected))
+        assert_that(yaml.safe_load(result), equal_to(expected))