Eagerly Init/Load FileSystem In Tez Task Containers

Initing/Loading FileSystem such as S3 can take ~10s - ~20s when called for the first time and the time taken for subsequent calls are negligable. If we can load the FileSystem much before it is used can help us to save some time. It can be especially useful in case of pre-warm Tez containers where the Tez task containers comes up when the Application Master (AM) is launched and not on-demand which is the default behavior. It can be also useful in cases where the Mapper tasks spends considerable time consuming the upstream shuffle data and then heads to process some FileSystem operations, in all such cases we have few FileSystem load up time.