Duplicate lines in machine agent log files

[Tim Penhey]

Hi folks,

Yes this is my fault.  An unintended consequence of a logging change before.

Now when you specify a log file and show log, it logs to both places.
Show log goes to stderr.

Upstart is real smart.

It puts the output from stdout and stderr into the logfile you specify.

I made --debug keep the current meaning, which is set the level to debug
and show the log.

So we are getting duplicate lines.

I have a branch that I'm just finishing up that will fix this.  Failing
that, it is a one line fix to the upstart/service.go to stop setting the
log file explicitly on the machine agent, and just let upstart handle it.

Tim