Continued Resource::Manger cleanup (JIRA RIPD-372)

 - Incorporates review comments from previous commit.
 - Increases Resource::Manager unit test coverage: verify a dropped consumer is blocked for a while.

I sympathize.  `n` is initialized on line 95, used in a while loop on line 96, and re-used without adjustment on line 113.  Both while loops have break conditions that don't show in the diff.  I made this change so it was easy to see the cumulative effects of the load as we passed through the warn phase up to the drop phase.  Using a single `n` for both loops made it easier to see the cumulative effects.  I would have hesitated more with non-unit test code, but this implementation gives me visibility of what I want to see in the unit test.