Fix: append to file through fuse doesn't always update file size.

git-svn-id: svn://irodssvn.ucsd.edu/trunk@5599 ea137bd6-aa86-47b6-b90d-b101d9f19a90
Make fuse always use fileSize from fileCache so that it is always up to date.

git-svn-id: svn://irodssvn.ucsd.edu/trunk@5600 ea137bd6-aa86-47b6-b90d-b101d9f19a90