AP_ICEngine: stop engine in E-Stop #38669

Job	Run time
build (base)	8m 49s
build (clang)	10m 36s
build-gcc-heli	9m 6s
autotest-heli (sitltest-heli)	14m 3s
autotest (sitltest-copter-tests1a)	11m 32s
autotest (sitltest-copter-tests1b)	13m 36s
autotest (sitltest-copter-tests1c)	15m 47s
autotest (sitltest-copter-tests1d)	13m 41s
autotest (sitltest-copter-tests1e)	13m 10s
autotest (sitltest-copter-tests2a)	13m 22s
autotest (sitltest-copter-tests2b)	32m 48s
	2h 36m 30s

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