LU-1861 osd: set proper type for compatibility files

LU-1861 osd: set proper type for compatibility files

The compatibility code in osd-ldiskfs uses osd_compat_add_entry()
to add dir entry for system files, but doesn't type in directory
entry properly so e2fsch complains about that.

Signed-off-by: Mikhail Pershin <tappro@whamcloud.com>
Change-Id: I8b1529b3303fba311432f4aa79d71afb6dc992d7
Reviewed-on: http://review.whamcloud.com/4669
Tested-by: Hudson
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>