[NCM] NCM Not Putting VPC States into Cache during PushGoalStatesStream

[zzxgzgz]

In
https://github.com/futurewei-cloud/alcor/blob/master/services/network_config_manager/src/main/java/com/futurewei/alcor/netwconfigmanager/service/impl/GoalStatePersistenceServiceImpl.java#L64

NCM didn't put VPC states into cache, which leads to retrieving a null VPC state, given a valid VPC_ID, during the on-demand workflow.