[ci] Fix test failure in API test (maintenance_test.rb)

The old test was not correct and the user never had the correct
permissions. So we needed to fix the old test case and tested for the
correct response code (:forbidden).

src/api/test/functional/maintenance_test.rb

@@ -965,8 +965,15 @@ def test_create_maintenance_project_and_release_packages
 
     # set an invalid
     post "/source/#{incidentProject}/_attribute", params: "<attributes><attribute namespace='OBS' name='EmbargoDate'><value>INVALID_DATE_STRING</value></attribute></attributes>"
+    assert_response :forbidden
+
+    # EmbargoDate is needed for test for releasing packages
+    login_king
+    post "/source/#{incidentProject}/_attribute", params: "<attributes><attribute namespace='OBS' name='EmbargoDate'><value>INVALID_DATE_STRING</value></attribute></attributes>"
     assert_response :success
 
+    prepare_request_with_user 'maintenance_coord', 'buildservice'
+
     # create some changes, including issue tracker references
     Timecop.freeze(1)
     put '/source/' + incidentProject + '/pack2.BaseDistro2.0_LinkedUpdateProject/dummy.changes', params: 'DUMMY bnc#1042'