Harness on success

In the case when all the OKs were successful the output is much shorter:

$ perl ../root/harness.pl tests/t11.pl

tests/t11.......ok
All tests successful.
Files=1, Tests=3,  0 wallclock secs
  ( 0.01 usr  0.00 sys +  0.01 cusr  0.01 csys =  0.03 CPU)
Result: PASS