LU-9782 osd-ldiskfs: avoid extra search

LU-9782 osd-ldiskfs: avoid extra search

Extent tree grow greatly durin random IO test with small block size.
osd_is_mapped responsible to large cpu consumption in this case.

|          |
|          |--94.49%-- ldiskfs_es_find_delayed_extent_range
|          |          ldiskfs_fiemap
|          |          osd_is_mapped
|          |          osd_declare_write_commit
|          |
|          |--5.49%-- ldiskfs_fiemap
|          |          osd_is_mapped
|          |          osd_declare_write_commit
|
|--21.80%-- ldiskfs_es_find_delayed_extent_range
|          |
|          |--100.00%-- ldiskfs_fiemap
|          |          osd_is_mapped

let's cache a osd_is_mapped result to avoid extra search in extent
tree,

Seagate-bug-id: MRP-4474
Signed-off-by: Alexey Lyashkov <alexey.lyashkov@seagate.com>
Change-Id: I63d480bfc7c6b7599b80ceeec9447b227a1610c8
Reviewed-on: https://review.whamcloud.com/28145
Reviewed-by: Fan Yong <fan.yong@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andrew Perepechko <andrew.perepechko@seagate.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>