Do not exit with non-zero return code if sysctl.conf or sysctl.conf.local files
are absent.

Approved by:	delphij
ext2fs: Translate the EXT4_EXTENTS and EXT4_INDEX to the inode flags.

r260545 cleared the inode flags to fix corruption problems but
we still need to pass some EXT4 flags for the ext4 read-only
mode.  None of these attributes has an equivalent in FreeBSD and
are uninteresting for the system utilities so they should be
innaccessible in ext2_getattrib().

Note: we also use EXT4_HUGE_FILE but we use it directly from the
dinode structure so it is not necessary to translate it,

Suggested by:	bde
MFC after:	3 days