example/passthrough_hp: Fix . and .. readdir lookup count

example/passthrough_hp: Fix . and .. readdir lookup count

Commit 170edc6a8ef0 added dot and dotdot (. and ..) to readdir
results, but introduced an issue when max number of entries
was reached - lookup count must not be decreased without
doing the lookup.
With ext4 as underlying file system readir seems to return . and ..
at random offsets and randomly failed xfstests for me.

This also fixes indentation, as passthrough_hp.cc does not follow
the linux indentation style (if we decide to fix this, it needs
to be done for the entire file).

Signed-off-by: Bernd Schubert <bschubert@ddn.com>