erp5_officejs_drone_simulator: fix loiter

See merge request !1817
Fix loitering trajectory when the drone is closer to the center than the required radius.
7 jobs for master in 0 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  External
failed ERP5.CodingStyleTest-Master

00:45:30

passed ERP5.PerformanceTest-Master

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failed ERP5.UnitTest-Master

01:30:36

failed ERP5.UnitTest-Zope2

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passed SlapOS.Eggs.UnitTest-Master.Python2

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passed SlapOS.Eggs.UnitTest-Master.Python3

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passed Wendelin.UnitTest-Master

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