health: Adding Smoke test

When using the SMOKE=<x_minutes> parameter on the command line, the
following scenario is engaged :

- benchmarking
- stress mode for x minutes
- benchmarking

The stress mode is made of the following series of tests
- all logical cores stressed by 128M memory access
- all logical cores stressed by some computation
- all disks drives stressed by IOs (4K random half of time, 1M
  sequential half of time)

All thoses tests are run for 1 minute and restart in loop.