LU-13309 osd-ldiskfs: speedup osd_bufs_get/put

LU-13309 osd-ldiskfs: speedup osd_bufs_get/put

Let's remove useless page processing
in osd_get_put/osd_put_page that affects regular I/O
in non-cached mode.

Change-Id: I1972cfdec940f104c1d66e1b1ffb4faa6007929b
Signed-off-by: Andrew Perepechko <c17827@cray.com>
Cray-bug-id: LUS-8004
Reviewed-on: https://review.whamcloud.com/37786
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alexander Zarochentsev <alexander.zarochentsev@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>