Fixed TACHYON-97

Current implementation of read(long position, byte[] buffer, int offset, int length) in HdfsFileInputStream is incomplete: 
1. It does not consider the boundary of file length, which could lead to an out of range issue when seeking the requested position in bytebuffer. 
2. It does not recover the original offset after function call.
@haoyuan I removed this part as @hsaputra suggested in our previously conversation.  

"With source control and version let's just remove it from file. No need to comment it out. 
We could always look at history to track the changes."