LU-16043 osc: allow error for write on CL_FSYNC_DISCARD

LU-16043 osc: allow error for write on CL_FSYNC_DISCARD

If case of CL_FSYNC_DISCARD error is allowed for write of osc object.

Otherwise, the included test fails in rm with:
  (osc_page.c:174:osc_page_delete()) Trying to teardown failed: -16
  (osc_page.c:175:osc_page_delete()) ASSERTION( 0 ) failed:
  (osc_page.c:175:osc_page_delete()) LBUG

Lustre-change: https://review.whamcloud.com/48032
Lustre-commit: 050c2fb23b1f98745305a3dfe3062ea5a66dfdb4

Test-Parameters: trivial testlist=sanity env=ONLY=907
HPE-bug-id: LUS-10410
Signed-off-by: Vladimir Saveliev <vladimir.saveliev@hpe.com>
Change-Id: I0aae0dc470ba0371964e7643a6d84b19a1b4e106
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Reviewed-by: Andrew Perepechko <andrew.perepechko@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/53009
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>