Sync tempest code from ceilometer

* https://review.openstack.org/530891 and https://review.openstack.org/527960
  are synced into telemetry-tempest-plugin

Change-Id: I6e099890aa03c9bd9b0039ce1e55a182886193e7
diff --git a/requirements.txt b/requirements.txt
index e966767..aa20603 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -7,5 +7,4 @@
 oslo.utils>=3.31.0 # Apache-2.0
 six>=1.10.0 # MIT
 tempest>=17.1.0 # Apache-2.0
-ujson
 gabbi>=1.30.0 # Apache-2.0
diff --git a/telemetry_tempest_plugin/aodh/service/client.py b/telemetry_tempest_plugin/aodh/service/client.py
index 39d2cf8..1043a05 100644
--- a/telemetry_tempest_plugin/aodh/service/client.py
+++ b/telemetry_tempest_plugin/aodh/service/client.py
@@ -13,11 +13,12 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import json
+
 from six.moves.urllib import parse as urllib
 from tempest import config
 from tempest.lib.common import rest_client
 from tempest import manager
-import ujson
 
 CONF = config.CONF
 
@@ -28,10 +29,10 @@
     uri_prefix = "v2"
 
     def deserialize(self, body):
-        return ujson.loads(body.replace("\n", ""))
+        return json.loads(body.replace("\n", ""))
 
     def serialize(self, body):
-        return ujson.dumps(body)
+        return json.dumps(body)
 
     def list_alarms(self, query=None):
         uri = '%s/alarms' % self.uri_prefix