Created by: DannyIsFunny

[Issue] Malloc will memset the malloced space automatically, which has caused that once mutable_data is called both virtual and physical memory will be occupied. After removing memset from Malloc<host> implementation, only virtual space will be created when tensor->mutable_data is applied, and the corresponding physical memory space will not be allocated until corresponding data is inputed. [Effect of Current PR] 500KB memory usage has been reduced (7MB in total ) on v45 model in our experiment on Android mobile