EX-7601 tgt: add remote_pages for writes

EX-7601 tgt: add remote_pages for writes

When we round a write to get all of the compressed chunks,
the number of local and the number of remote pages will
differ.  We need to make sure we do the checksum and data
transfer using the number of remote pages, not the number of
local pages.

This patch calculates the number of remote pages and uses it
accordingly.

Note that just like on the read side, this patch doesn't do
anything until we're actually rounding the chunks for IO in
a later patch.

Signed-off-by: Patrick Farrell <pfarrell@whamcloud.com>
Change-Id: I38256070d68246613ce67b0bfe328f6443a95533
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/52964
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>