LU-13513 osp: make neterr not fatal for precreate_reserve

LU-13513 osp: make neterr not fatal for precreate_reserve

When OST_CREATE (not resendable rpc) sent by precreate thread fails
with network error, osp_pre_update_status() sets d->opd_pre_status to
EIO. osp_precreate_reserve() considers EIO as fatal and does not wait
for another attempt from precreate thread. That may make
mdt_intent_open() to return ENOSPC confusing a caller.  ENOSPC comes
from lod_alloc_rr().

osp_precreate_send(): in case of network error switch EIO to ENOTCONN.

Test to illustrate the issue is added.

Lustre-change: https://review.whamcloud.com/38472
Lustre-commit: 4bba67075aa3d8739d8ca99642ff2b2836774479

Cray-bug-id: LUS-8811
Signed-off-by: Vladimir Saveliev <c17830@cray.com>
Change-Id: Iffaad9bd16f216f758c784b708e21b525c999b14
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/46179
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>