support benchmark action timeout

[kwmonroe]

We currently run the benchmark actions with timeout = -1 (no timeout). If we're hung, this will stall cwr forever. It would be nice if we could add a key to either the benchmark definition (to specify timeout per benchmark) or an overall testplan benchmark timeout (to specify a timeout for all benchmarks if/when multiple actions are supported in cwr).

[seman]

Currently, the timeout is set to 1 hr and won't run forever. Changing this to enhancement for adding a timeout key in a test plan.