LU-14205 osd-ldiskfs: fix return of osd_extend_restart_trans()

LU-14205 osd-ldiskfs: fix return of osd_extend_restart_trans()

ldiskfs_journal_ensure_credits() could possibly return 1 if
transaction restarted, Lustre osd expect it return 0 or negative.

Fixes: cf48a2d23b ("LU-13839 kernel: RHEL 8.3 server support")
Signed-off-by: Wang Shilong <wshilong@ddn.com>
Change-Id: I51ff0bd50575902b66529cbd71ff14710c202d03
Reviewed-on: https://review.whamcloud.com/40989
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>