cam_idx vs img_idx

#### Issue details
During the flight the camera return markings appear on the map, but their value shown when hovering the mouse over it shows the number of the camera trigger. Is it possible to invert this information?

#### Version
any

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

#### Airframe type
any

#### Hardware type
pixhawk

#### Logs
no log. Just answare about code.

Start by reproducing the Copter map behavior described in the issue and inspect the code responsible for camera return markings and their hover values. Confirm whether the displayed value is cam_idx or img_idx, then verify that the hover text matches the requested marking after the change.

Written by the indexing model from the issue text.