LU-13799 llite: Remove transient page counting

LU-13799 llite: Remove transient page counting

Transient page counting is not used for anything, as
already noted in the commit message, but costs something
like 4% of the time in DIO page submission.

Remove it.

mpirun -np 1  $IOR -w -r -t 64M -b 64G -o ./iorfile --posix.odirect

This patch reduces i/o time in ms/GiB by:
Write: 6 ms/GiB
Read: 11 ms/GiB

Totals:
Write: 174 ms/GiB
Read: 167 ms/GiB

With previous patches in series:
write     5703 MiB/s
read      5756 MiB/s

Plus this patch:
write     5900 MiB/s
read      6136 MiB/s

Lustre-change: https://review.whamcloud.com/39441
Lustre-commit: 587e5aa8342980f761930235714add1cca80686b

Signed-off-by: Patrick Farrell <farr0186@gmail.com>
Change-Id: I825de4f1b5d1dd1476a4a711bfa51e7d24b5027a
Reviewed-on: https://review.whamcloud.com/44444
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>