[FIXED JENKINS-29568] A better fix

- 252e1296 doesn't work for all cases as there are code paths
  where a pending launch can be removed from the pending list and not have spent() called.
- There was no reason for iterating the list twice anyway, as all of this takes place with the locks held
- My notifying each one as we process, if there is an Error, we will not leave any stranded. The next run
  through, if there is one, will cover those instances.

(cherry picked from commit 4f0ca16b)