Improve output on Clock Jitter test failure

[Jeff Lane ]

When the jitter test fails, the output can be a bit unfriendly:

Testing for clock jitter on 96 cpus
ERROR, jitter = 0.288711
iter = 2549, cpus = 0,95
FAILED: 1 iterations failed

This could stand some improvements.

[Jeff Lane  (bladernr)]

Updated output is a little more informative:

$ ./clocktest
Testing for clock jitter on 8 cpus
ERROR: jitter = 0.010292 Jitter must be < 0.2 to pass
ERROR: Failed Iteration = 72, Slowest CPU: 0 Fastest CPU: 7
FAILED: 1 iterations failed