First GPS Origin set messes up the Vehicles altitude

that's likely because we are sending it as zero here:
https://github.com/bluerobotics/BlueOS-Water-Linked-DVL/blob/master/dvl-a50/mavlink2resthelper.py#L134

User reported the issue [here](https://discuss.bluerobotics.com/t/depth-reading-changes-in-qgc-when-geolocation-inputted/18741/3)

Start at dvl-a50/mavlink2resthelper.py line 134 and read the linked Blue Robotics discussion for the reported GPS-origin behavior. Trace the value sent there and how it affects the vehicle altitude. Done means setting the first GPS origin no longer causes the altitude problem described in the report.

Written by the indexing model from the issue text.