AP_Camera: fix video recording while armed #28185

Job	Run time
build (chibios, Durandal)	17m 6s
build (chibios, MatekF405)	15m 21s
build (chibios, KakuteF7)	14m 9s
build (chibios, MatekH743-bdshot)	16m 29s
build (chibios, Pixhawk1-1M)	14m 40s
build (chibios, MatekF405-CAN)	1m 43s
build (chibios, DrotekP3Pro)	2m 38s
build (chibios, Hitec-Airspeed)	3m 19s
build (chibios, f103-GPS)	3m 23s
build (disco, armhf)	14m 22s
	1h 43m 10s

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