mission_raw: fix upload race condition #3947

Job	Run time
coverage (ubuntu-20.04)	5m 5s
alpine 3.19.0 (musl)	9m 56s
Ubuntu/Debian packaging (Ubuntu 20.04)	7m 53s
ubuntu-20.04 (package, non-mavsdk_server)	6m 40s
ubuntu-22.04 (package, non-mavsdk_server)	5m 57s
android-arm	5m 41s
linux-armv6	4m 56s
android-arm64	5m 47s
linux-armv6-musl	10m 23s
ios	8m 21s
android-x86	5m 34s
linux-armv7l-musl	10m 17s
ios_simulator	8m 31s
linux-arm64-musl	11m 13s
android-x86_64	5m 46s
linux-armv7	5m 2s
linux-arm64	5m 18s
ubuntu-20.04 (mavsdk, hunter)	4m 2s
macOS	12m 24s
ubuntu-20.04 (non-mavsdk_server, non-superbuild)	5m 27s
macOS-framework	15m 44s
ubuntu-22.04 (style and proto check)	1m 46s
ubuntu-20.04 (mavsdk_server, superbuild)	12m 29s
Windows	12m 43s
ubuntu-22.04 (mavsdk_server, superbuild)	10m 43s
iOS XCFramework	56s
	3h 18m 34s

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