Backport IMU Covariances to ROS Iron

[wittenator]

Desired behavior

I would like to also have covariance data in IMU messages in ROS Iron if I build the Iron branch from source.

Alternatives considered

None

Implementation suggestion

Would it be possible to backport the conditional covariance filling in IMU messages to the Iron branch?

[azeey]

I don't think there's a reason for not backporting it. Would you be able to open a PR?

[wittenator]

Sure thing, I created a PR for that.

[azeey]

Fixed by #375.