LU-9740 ldiskfs: more credits for non-append write

LU-9740 ldiskfs: more credits for non-append write

As code comment explained: for not append write, the split
may need to modify existing blocks moving entries into the
new ones. That needs more journal credits. The old logic
handled it as append case by typo.

Lustre-change: https://review.whamcloud.com/27947
Lustre-commit: c668a8d405a9d8819bf9b96e0c610ccc5353d77d

Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: I277f144ec056bb2f07ffd5e5ce19d9a6eee8e0ef
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Minh Diep <minh.diep@intel.com>
Reviewed-on: https://review.whamcloud.com/28229
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>