Fix stdio permission error in userns container #6884

Job	Run time
cross-i386	1m 7s
test (ubuntu-20.04, 1.22.x, rootless, -race)	6m 0s
test (ubuntu-20.04, 1.22.x, rootless)	5m 46s
test (ubuntu-20.04, 1.22.x, -race)	7m 55s
test (ubuntu-20.04, 1.22.x)	7m 10s
test (ubuntu-20.04, 1.23.x, rootless, -race)	6m 6s
test (ubuntu-20.04, 1.23.x, rootless)	5m 40s
test (ubuntu-20.04, 1.23.x, -race)	8m 10s
test (ubuntu-20.04, 1.23.x)	7m 13s
test (ubuntu-20.04, 1.23.x, criu-dev)	8m 14s
test (ubuntu-24.04, 1.22.x, rootless, -race)	5m 50s
test (ubuntu-24.04, 1.22.x, rootless)	5m 9s
test (ubuntu-24.04, 1.22.x, -race)	7m 34s
test (ubuntu-24.04, 1.22.x)	6m 45s
test (ubuntu-24.04, 1.23.x, rootless, -race)	5m 19s
test (ubuntu-24.04, 1.23.x, rootless)	5m 2s
test (ubuntu-24.04, 1.23.x, -race)	8m 19s
test (ubuntu-24.04, 1.23.x)	8m 12s
test (ubuntu-24.04, 1.23.x, criu-dev)	7m 57s
test (actuated-arm64-6cpu-8gb, 1.23.x, rootless)	6m 3s
test (actuated-arm64-6cpu-8gb, 1.23.x)	7m 52s
all-done	0s
	2h 17m 23s

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