Decrease rpc getFileStatus count when open a storefile (cache filestatus in storefileinfo rather than load each time)

When a store needs to open a storefile , it will create getFileStatus rpc twice or more . So open a region with too many files or open too many regions at once will cost very much time. if namenode wastes too much time in rpc process every time (in my case 5s sometime) due to namenode itself's problem . So i think we can descrease the times for getFileStatus , this will reduce stress to namenode and consume less time when store open a storefile .