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.

Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: I277f144ec056bb2f07ffd5e5ce19d9a6eee8e0ef
Reviewed-on: https://review.whamcloud.com/27947
Tested-by: Jenkins
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>