#1 User-Agent fixed

[Mark Nottingham]

Httperf will always emit the httperf user-agent, even when set explicitly in arguments. This makes it difficult to test when UA is important to the server.

Two possible fixes;

1) make it possible to explicitly override the UA on the command line. It would probably also be necessary to allow logs (e.g., wlog) to override it.

2) omit the UA, unless it's specified.

#2 is probably easier, but may cause problems if people don't remember to set a UA.