Fix stdio permission error in userns container #6869

Job	Run time
cross-i386	3m 38s
test (ubuntu-20.04, 1.22.x, rootless, -race)	30m 14s
cross-i386 (runc_nodmz)	3m 44s
test (ubuntu-20.04, 1.22.x, rootless)	30m 13s
test (ubuntu-20.04, 1.22.x, -race)	4m 37s
test (ubuntu-20.04, 1.22.x)	3m 43s
test (ubuntu-20.04, 1.23.x, rootless, -race)	30m 14s
test (ubuntu-20.04, 1.23.x, rootless)	30m 15s
test (ubuntu-20.04, 1.23.x, -race)	4m 43s
test (ubuntu-20.04, 1.23.x)	4m 19s
test (ubuntu-20.04, 1.23.x, criu-dev)	4m 43s
test (ubuntu-24.04, 1.22.x, rootless, -race)	30m 13s
test (ubuntu-24.04, 1.22.x, rootless)	30m 14s
test (ubuntu-24.04, 1.22.x, -race)	4m 27s
test (ubuntu-24.04, 1.22.x)	3m 41s
test (ubuntu-24.04, 1.23.x, rootless, -race)	30m 14s
test (ubuntu-24.04, 1.23.x, rootless)	30m 15s
test (ubuntu-24.04, 1.23.x, -race)	4m 48s
test (ubuntu-24.04, 1.23.x)	4m 11s
test (ubuntu-24.04, 1.23.x, runc_nodmz)	4m 22s
test (ubuntu-24.04, 1.23.x, criu-dev)	4m 52s
test (actuated-arm64-6cpu-8gb, 1.23.x, rootless)	30m 8s
test (actuated-arm64-6cpu-8gb, 1.23.x)	3m 54s
all-done	0s
	5h 31m 42s

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