statemachine: error during sleeps should not override sleep time

[schmichael]

Right now the following can occur:

• Task goes to sleep at 1am until 3am
• Task has an error at 2am*
• Default error handler is used which retries the work at 2:10am

Now instead of running at 3am, the work has run at 2:10am.

The statemachine should make a best effort to wait until 3am to run the work.

* Yes, even sleeping work can suddenly return an error. Its command watcher could fail, or the work could get rebalanced and loading the state could fail.