Switch remaining json import to oslo_serialization

While switching json to oslo_serialization, there were some
usage of json left which are caught while implementing UT for
service clients.

- http://logs.openstack.org/73/214073/4/check/gate-tempest-python34/0976c0c/testr_results.html.gz

This commit switch all remaining json usage to jsonutils of
oslo_serilization

Change-Id: Icb38fd22c61545cfbe024108a06068ada01afc6b

tempest/services/compute/json/floating_ip_pools_client.py

@@ -13,8 +13,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import json
-
+from oslo_serialization import jsonutils as json
 from six.moves.urllib import parse as urllib
 
 from tempest.api_schema.response.compute.v2_1 import floating_ips as schema

tempest/services/compute/json/floating_ips_bulk_client.py

@@ -13,7 +13,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import json
+from oslo_serialization import jsonutils as json
 
 from tempest.api_schema.response.compute.v2_1 import floating_ips as schema
 from tempest.common import service_client

tempest/services/compute/json/security_group_rules_client.py

@@ -13,8 +13,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import json
-
+from oslo_serialization import jsonutils as json
 from tempest_lib import exceptions as lib_exc
 
 from tempest.api_schema.response.compute.v2_1 import security_groups as schema

tempest/services/compute/json/server_groups_client.py

@@ -14,7 +14,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import json
+from oslo_serialization import jsonutils as json
 
 from tempest.api_schema.response.compute.v2_1 import servers as schema
 from tempest.common import service_client