src: fix deadlock in NodePlatform::DrainTasks on process shutdown #3601

Job	Run time
Build slim tarball	3m 12s
x86_64-darwin: with shared libraries	34m 22s
aarch64-darwin: with shared libraries	22m 23s
aarch64-linux: with shared libraries	21m 26s
x86_64-linux: with shared libraries	25m 42s
	1h 47m 5s

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