smaccmpilot: sensors task initializes in loop, not in taskInit

* initialization takes about 6 seconds in a blocking external call
  to the APM code
* by running this in the event loop, it allows the rest of our code
  to work while the sensors are booting
* however, it means the sensors task will break its periodic schedule, which is
  not generally desired. in this case we just have to let it go until we
  can rewrite the sensor drivers for tower