controllers.flight: move get_flight_path() to a global function
controllers.flight: move get_flight_path() to a global function

To be reused.

dkm/skylines,shadowoneau/skylines,TobiasLohner/SkyLines,snip/skylines,TobiasLohner/SkyLines,TobiasLohner/SkyLines,snip/skylines,Turbo87/skylines,skylines-project/skylines,shadowoneau/skylines,dkm/skylines,RBE-Avionik/skylines,dkm/skylines,Harry-R/skylines,RBE-Avionik/skylines,dkm/skylines,skylines-project/skylines,RBE-Avionik/skylines,Turbo87/skylines,Harry-R/skylines,kerel-fs/skylines,RBE-Avionik/skylines,Harry-R/skylines,Harry-R/skylines,shadowoneau/skylines,skylines-project/skylines,kerel-fs/skylines,skylines-project/skylines,shadowoneau/skylines,snip/skylines,kerel-fs/skylines,Turbo87/skylines,Turbo87/skylines