patchperf-lib: fix start/stop of perf tests

> ae75342 test-lib: rearrange start/end of test_expect_* and test_skip
> changed the way tests are started/stopped, but did not update the perf
> tests.  They were therefore giving the wrong output, because of the
> wrong test count.  Fix this by starting and stopping the tests
> correctly.
>
> Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>

>  t/perf/perf-lib.sh | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/t/perf/perf-lib.sh b/t/perf/perf-lib.sh
> index a816fbc..c61d535 100644
> --- a/t/perf/perf-lib.sh
> +++ b/t/perf/perf-lib.sh
> @@ -150,6 +150,7 @@ exit $ret' >&3 2>&4
>  
>  
>  test_perf () {
> +	test_start_
>  	test "$#" = 3 && { test_prereq=$1; shift; } || test_prereq=
>  	test "$#" = 2 ||
>  	error "bug in the test script: not 2 or 3 parameters to test-expect-success"
> @@ -187,7 +188,7 @@ test_perf () {
>  		base="$perf_results_dir"/"$perf_results_prefix$(basename "$0" .sh)"."$test_count"
>  		"$TEST_DIRECTORY"/perf/min_time.perl test_time.* >"$base".times
>  	fi
> -	echo >&3 ""
> +	test_finish_
>  }
>  
>  # We extend test_done to print timings at the end (./run disables this