"git-apply --check" should not report "fixed"

When running "git apply --check" while --whitespace=fix is enabled (either from the command line or via the configuration), we reported that "N line(s) applied after _fixing_", but --check by itself does not apply and this message was alarming. We could even reword the message to say "N line(s) would have been applied after fixing...", but this patch does not go that far. Instead, we just make it use the "N lines add whitespace errors" warning, which happens to be a good diagnostic message a user would expect from the --check option. Signed-off-by: Junio C Hamano <gitster@pobox.com>