sbin/newfs_hammer: Set HAMMER_OBJTYPE_DIRECTORY for ondisk PFS#0 data

sbin/newfs_hammer: Set HAMMER_OBJTYPE_DIRECTORY for ondisk PFS#0 data

Ondisk PFS data is a record part of the root ip (inode) when
a new PFS is created via ioctl, so it's normal for ondisk PFS
data to have HAMMER_OBJTYPE_DIRECTORY for obj_type. It's
rather insane that PFS#0 (the only PFS created without ioctl)
has 0 (HAMMER_OBJTYPE_UNKNOWN) for obj_type while the root ip
(not PFS root but HAMMER root) is apparently a directory.

Although PFS#0 and the rest of the PFS are a bit different,
PFS ioctls treat all the ondisk PFS data in the same fashion.
Having consistent obj_type value for the same data type is
considered better than not having.

This change does affect 1 byte of ondisk PFS#0 data initially
created by newfs_hammer, but doesn't break compatibility.
Also see hammer_mkroot_pseudofs().