[bugfix] mcreate with error should fail for a reason

auth.feature

@@ -20,7 +20,7 @@ Feature: User management
     And I log in as 'my-user-name':'my-user-pwd'
     And I update my user custom data with the pair <field-name>:<field-value>
     When I get my user info
-    Then the response '_source' field contains the pair <field-name>:<field-value>
+    Then the response 'content' field contains the pair <field-name>:<field-value>
     Examples:
       | field-name | field-value |
       | 'my_data' | 'mystringvalue' |

documents.feature

@@ -143,6 +143,7 @@ Feature: Document management
     Given Kuzzle Server is running
     And there is an index 'test-index'
     And it has a collection 'mcreate-test-collection'
+    And the collection has a document with id 'mcreate-my-document-id'
     When I create the documents ['mcreate-my-document-id', 'mcreate-my-document-id2']
     Then I must have 2 documents in the collection
     And I get a partial error