LU-14729 osd-ldiskfs: declare dirty block groups correctly

LU-14729 osd-ldiskfs: declare dirty block groups correctly

Calculate dirty block groups only include estimated extents,
indirect blocks and extent node/leaf blocks are missed, this
could make us short of credits.

Lustre-change: https://review.whamcloud.com/43890
Lustre-commit: 42cda8781f94ad1138afac2d23180ea48f3c3450

Fixes: 0271b17b80a82 ("LU-14134 osd-ldiskfs: reduce credits for new writing")
Signed-off-by: Wang Shilong <wshilong@ddn.com>
Change-Id: Iec8525823b04e909c030f94bf75b8eca60d31c50
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/45506
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Li Dongyang <dongyangli@ddn.com>
Tested-by: Andreas Dilger <adilger@whamcloud.com>