Add --log-level support - Issue #5198

I noticed that even if I set the log level to 'fatal' there are still quite a few things printed to stdout/err.
In my quick scan its because not everything is using the default logger.  For example, I noticed that
job.go has its own.  I think that should be removed and everyone should use the same logger.
I could move that change into this PR if people want, but I'd prefer to split it out into a new one so that
this one is just focused on adding the --log-level flag.

Closes #5198

Signed-off-by: Doug Davis <dug@us.ibm.com>
Okay, what about if you'll write this code when we'll update logrus in our repo to logrus with level more verbose than debug? I think it worth to keep code simplier for pretty small chance to bring small bug with logrus update in far future.