Add --log-level support

Next steps, in another PR, would be:
- make all logging go through the logrus stuff
- I'd like to see if we can remove the env var stuff (like DEBUG) but we'll see

Closes #5198

Signed-off-by: Doug Davis <dug@us.ibm.com>
Merge pull request #8335 from duglin/Issue5198

Add --log-level support - Issue #5198