LU-8465 e2fsck: cleanup struct e2fsck_struct

LU-8465 e2fsck: cleanup struct e2fsck_struct

Fields of "struct e2fsck_struct" are seperated into
different types according to how these fields will be
used when parallel fsck is enabled.

remove unused @abort_code

Change-Id: Ic89398cca70e0833ecb8fe6aae24c1e99e5a9e90
Signed-off-by: Li Xi <lixi@ddn.com>
Signed-off-by: Wang Shilong <wshilong@ddn.com>
Reviewed-on: https://review.whamcloud.com/35684
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>