agent: remove unnecessary sleep from tests
Merge pull request #829 from jonboulle/agent_tests

agent: remove unnecessary sleep from tests
agent: further work towards purging "Job" terminology

- Update agent.loadJob/startJob etc
- Switch taskChain to job.Unit
- Update task reasons
- Update tests
agent: further job-removal work

Simplify currentAgentState dramatically; all it really needs is a
mapping from unit names to their states, so switch to that.

Rename and modify agent.jobs() --> agent.units() accordingly.