LU-15993 ofd: don't leak pages if nodemap fails

ofd_commitrw() shouldn't exit w/o calling ofd_commitrw_write(),
otherwise the pages taken in ofd_preprw() are leaked.

same in mdt_obd_commitrw()

Fixes: bbfdc7c167 ("LU-14739 quota: fix quota with root squash enabled")

Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Change-Id: Icd60c7ab80c5a7b65603d7da0d2e83872dc6b97f
Reviewed-on: https://review.whamcloud.com/47873
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>