EX-7601 osc: only set compressed flag on compressed pages

EX-7601 osc: only set compressed flag on compressed pages

The code accidentally sets the compressed flag on all
pages processed through fill_cpga, even if they're not
compressed.  Oops.

Also stop setting pg->index on the pages in the compressed
pga, this is only used by encryption and that's no longer
supported with compression.

Signed-off-by: Patrick Farrell <pfarrell@whamcloud.com>
Change-Id: I313fd943a18b71cd52493852a6884f30d187e52f
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/53118
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Artem Blagodarenko <ablagodarenko@ddn.com>