pNFS: honor clora_changed when recalling a layout

When the metadata server recalls a layout with clora_changed FALSE, the
layout is not changing and the client may complete its modified writes to
the storage devices before returning the layout (RFC 8881, Section
20.3.3).  Only when clora_changed is TRUE -- the server is restriping, or
a storage device has failed -- should the client stop writing to the
storage devices and redirect through the metadata server.

Since commit b739a5bd9d9f ("NFSv4/flexfiles: Cancel I/O if the layout is
recalled or revoked") the client cancels in-flight I/O on every recall,
regardless of clora_changed.  For an unchanged recall this abandons
writes whose data may already have reached the storage device; such a
write can then land after the LAYOUTRETURN, which the server sees as a
write without a layout.

Pass the recall's clora_changed value through
pnfs_mark_matching_lsegs_return() and only cancel in-flight I/O when the
layout is actually changing.  When it is not, the existing deferred
return path waits for the in-flight writes to drain before sending the
LAYOUTRETURN.  Other callers, which are tearing down or returning the
layout for their own reasons, continue to cancel as before.

Signed-off-by: Benjamin Coddington <bcodding@hammerspace.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

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