Climb was not stopping when start was already over the asked optimal altitude/flight level

[christophe-david]

In mission, when asking a climb up to an optimal altitude/flight level (i.e. where the maximum CL is achieved), if the maximum CL was achieved for a lower altitude than the starting one, the climb was not stopped until hard limits were attained (the 40000m hard-coded limit, or possibly a crash of the propulsion model).

This PR fixes this problem.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 84.52%. Comparing base (f985c4b) to head (dd36d0b). Report is 30 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #526 +/- ## ======================================= Coverage 84.52% 84.52% ======================================= Files 138 138 Lines 6267 6268 +1 Branches 908 909 +1 ======================================= + Hits 5297 5298 +1 Misses 816 816 Partials 154 154 ```

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