LU-16637 llite: tolerate fresh page cache pages after truncate

LU-16637 llite: tolerate fresh page cache pages after truncate

Truncate called by ll_layout_refesh() can race with a fast read
or tiny write, which can add an uninitialized non-uptodate page
into the page cache.

We want to avoid expensive locking for this rare case so if there
is any leftover in the cache after truncate, just check that
the pages are not uptodate, not dirty and do not have any
filesystem-specific information attached to them.

Change-Id: I8cadc022a3d1822a585f32e1a765e59ad0ff434d
Signed-off-by: Andrew Perepechko <andrew.perepechko@hpe.com>
HPE-bug-id: LUS-11937