Minor test refactoring

[#69544442]
Signed-off-by: Kai Zhang <kaizhang@cn.ibm.com>
Refactor stagings_controller.

Signed-off-by: Kai Zhang <kaizhang@cn.ibm.com>
Finish StagingsController refactoring

[#69544442]

Signed-off-by: Kai Zhang <kaizhang@cn.ibm.com>