pnfs/blocklayout: don't set pages uptodate

The core nfs code handles setting pages uptodate on reads, no need to mess
with the pageflags outselves.  Also remove a debug function to dump page
flags.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>