Correct two bugs in fsck_ffs(8) triggered by corrupted filesystems.

Always create a directory inode structure when a directory inode is
found in Pass 1 as it is not known whether it will be saved or removed
in later passes. If it is to be saved the directory inode structure
is needed to track its status and fsck_ffs(8) will segment fault if
it does not exist.

Reported-by: Robert Morris
PR: 271310
PR: 271354
MFC-after: 1 week
Sponsored-by: The FreeBSD Foundation