initializeOnce in IMU: relax self-test check

[rgatkinson]

When checking for self-test results, it should only look at components that the mode we're going to set actually uses. E.g.: if we're not going to use the compass, we shouldn't care if it self tests correctly.

We've had reports of compasses (ie: magnetometers) acting up in the self test check, preventing successful initialization, and this would work around the problem