c1795bb0

 (Unify whitespace checking) incorrectly made the
checking function return without incrementing the line numbers
when there is no whitespace problem is found on a '+' line.

This resurrects the earlier behaviour.

Noticed and reported by Jay Soffian.  The test script was stolen
from Jay's independent fix.

Signed-off-by: Junio C Hamano <gitster@pobox.com>