accel cal is unclear

While waiting for the initial gyro cal for accel cal (3D cal) there is no message displayed, which makes it seem that it is stuck.
It would be good to have a "waiting for vehicle to be still ..." message

See this user question:
https://discuss.ardupilot.org/t/plane-4-0-accelerometer-calibration-does-not-do-anything/48686

Start by reproducing the accelerometer calibration flow described in the issue and trace the Mission Planner UI path used while the initial gyro calibration is pending. Done means the interface displays a clear “waiting for vehicle to be still ...” message instead of appearing stuck; no source file or test is named in the issue.

Written by the indexing model from the issue text.