capabilities: be more graceful in resetting ambient #7353

Job	Run time
cross-i386	2m 44s
test (ubuntu-20.04, 1.22.x, rootless, -race)	7m 11s
test (ubuntu-20.04, 1.22.x, rootless)	6m 56s
test (ubuntu-20.04, 1.22.x, -race)	7m 49s
test (ubuntu-20.04, 1.22.x)	7m 22s
test (ubuntu-20.04, 1.23.x, rootless, -race)	7m 15s
test (ubuntu-20.04, 1.23.x, rootless)	7m 2s
test (ubuntu-20.04, 1.23.x, -race)	8m 9s
test (ubuntu-20.04, 1.23.x)	7m 5s
test (ubuntu-20.04, 1.23.x, criu-dev)	7m 43s
test (ubuntu-24.04, 1.22.x, rootless, -race)	10m 28s
test (ubuntu-24.04, 1.22.x, rootless)	9m 36s
test (ubuntu-24.04, 1.22.x, -race)	7m 41s
test (ubuntu-24.04, 1.22.x)	6m 53s
test (ubuntu-24.04, 1.23.x, rootless, -race)	9m 42s
test (ubuntu-24.04, 1.23.x, rootless)	10m 23s
test (ubuntu-24.04, 1.23.x, -race)	7m 53s
test (ubuntu-24.04, 1.23.x)	8m 27s
test (ubuntu-24.04, 1.23.x, criu-dev)	7m 58s
test (actuated-arm64-6cpu-8gb, 1.23.x, rootless)	11m 35s
test (actuated-arm64-6cpu-8gb, 1.23.x)	7m 51s
all-done	1s
	2h 47m 44s

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