stop compass cal on ground if compass learn is set to 3

#### Issue details
found a niche bug where if compass_learn is set to 3 then it makes it look like you can start a ground calibration, but doesnt show the 0%,
So something like if you try to press 'start' and your param is set, then it should give some info to the user...

#### Version
1.3.77

#### Platform
[ ] All
[ ] AntennaTracker
[ ] Copter
[ ] Plane
[ ] Rover
[ ] Sub

#### Airframe type
_What type of airframe (flying wing, glider, hex, Y6, octa etc)_

#### Hardware type
_What autopilot hardware was used? (pixhawk, pixracer, PX4FMU etc)_

#### Logs
_Please provide a link to any relevant logs that show the issue_

Start by reproducing the ground compass calibration flow in Mission Planner with compass_learn set to 3, then inspect the code handling the calibration start action and its user-facing status. Done means pressing Start does not present a misleading calibration flow and instead gives the user clear information about the parameter setting.

Written by the indexing model from the issue text.