Supporting tags in KMS (#2332)

The CreateKey API method accepts tags but does not return them.

moto/kms/responses.py

@@ -31,9 +31,10 @@ class KmsResponse(BaseResponse):
         policy = self.parameters.get('Policy')
         key_usage = self.parameters.get('KeyUsage')
         description = self.parameters.get('Description')
+        tags = self.parameters.get('Tags')
 
         key = self.kms_backend.create_key(
-            policy, key_usage, description, self.region)
+            policy, key_usage, description, tags, self.region)
         return json.dumps(key.to_dict())
 
     def update_key_description(self):