When DO_REPOSITION asked for a change into GUIDED and the mode change
was refused (for example GUIDED being blocked by FLTMODE_GCSBLOCK) the
result of set_mode() was ignored. The requested location was still
loaded with set_guided_WP() and the command was ACCEPTED, so a vehicle
in AUTO stayed in AUTO but flew towards the reposition target.
Return MAV_RESULT_FAILED instead, leaving the current mode's navigation
alone.
Peter Barker
0d3e2aaa8e