Don't unset the job submit ID when a task is done.

This caused occasional failures in the events/task test suite: if a task
reported in succeeded while a poll command was in progress, the poll
result would set the task back to 'running', but the 'task succeeded'
message just prior to that had unset the submit ID thereby preventing
the next poll from correcting the problem.
Fixed T-N cycle offset bug for n > 24 (HoursOfTheDay cycling)

Example:
[[[0]]]
    graph = "foo[T-36] = bar"
This graph results in bar triggering off foo at T-36; but it is also
used to infer that one of the valid cycle hours of foo is 0z minus 36,
or 18z. Conversion of T-N back to the 0-23 range was broken for N > 24
with the result that foo could sometimes spawn into the wrong cycle.
No change - to NOTE that previous commit message contains an error.

(replace 36 with 30 - this was just a typo in the commit message).
Merge pull request #492 from hjoliver/no-submit-id-unset

Don't unset the job submit ID when a task is done.
Merge pull request #496 from hjoliver/BugFix.HoursOfTheDay-cycling

Fixed T-N cycle offset bug for n > 24 (HoursOfTheDay cycling)