LU-12651 osc: always call update_next_shrink

LU-12651 osc: always call update_next_shrink

Call update_next_shrink in case of clients not
supporting grant shrinking or clients with grant
shrinking explicitely disabled. Otherwise
osc_grant_work_handler() schedules itself immediately
after its completion causing excessive CPU consumption.

Fixes: 3e070e30a98d ("LU-8708 osc: enable/disable OSC grant shrink")

Lustre-change: https://review.whamcloud.com/37429
Lustre-commit: 117f587bc3e60f4dd1c939f8488e43cb752c12ca

Cray-bug-id: LUS-8460
Change-Id: I507b3d10dd5374772456853098bc26053cbd140d
Signed-off-by: Alexander Zarochentsev <c17826@cray.com>
Reviewed-by: Andrew Perepechko <c17827@cray.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Vladimir Saveliev <c17830@cray.com>
Signed-off-by: Minh Diep <mdiep@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/37572
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>