#2 Option to abort if there are errors

[Mark Nottingham]

For some users, interpreting httperf's output can be difficult.

Since a large part of doing so is assuring that the test ran successfully (i.e., there were no client-side errors), it strikes me that it would simplify things considerably if we added a command-line flag that, when present, would instruct httperf to abort with an appropriate complaint if;

a) total CPU is less than, say, 90%, or
b) any errors *other than* client-timeout are seen

This would make it signifiacantly easier for operators to interpret the output.

Optionally, if the flag is present and the test run is successful, we could suppress the CPU and error information (perhaps just leaving the total), to make output cleaner.