LU-14769 e2fsck: init inode_badness proper for thread context

LU-14769 e2fsck: init inode_badness proper for thread context

Some bad inode might be added before pass1, so global_ctx's
@inode_badness might be not NULL, we need init thread_ctx's
inode badness as NULL.

Change-Id: I31a526fd0cfc0c9f8c13598deba4ae882080412f
Signed-off-by: Wang Shilong <wshilong@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/44012
Reviewed-by: Wang Shilong <wshilong@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>