libct/int: retry Checkpoint for cgroup v1 #7112

Job	Run time
test (ubuntu-20.04, 1.22.x, rootless, -race)	7m 33s
test (ubuntu-20.04, 1.22.x, rootless)	6m 40s
test (ubuntu-20.04, 1.22.x, -race)	7m 51s
test (ubuntu-20.04, 1.22.x)	6m 59s
test (ubuntu-20.04, 1.23.x, rootless, -race)	7m 35s
test (ubuntu-20.04, 1.23.x, rootless)	6m 55s
test (ubuntu-20.04, 1.23.x, -race)	8m 3s
test (ubuntu-20.04, 1.23.x)	7m 20s
test (ubuntu-20.04, 1.23.x, criu-dev)	7m 53s
cross-i386	1m 19s
test (ubuntu-24.04, 1.22.x, rootless, -race)	9m 31s
test (ubuntu-24.04, 1.22.x, rootless)	9m 32s
test (ubuntu-24.04, 1.22.x, -race)	7m 54s
test (ubuntu-24.04, 1.22.x)	6m 56s
test (ubuntu-24.04, 1.23.x, rootless, -race)	9m 54s
test (ubuntu-24.04, 1.23.x, rootless)	9m 28s
test (ubuntu-24.04, 1.23.x, -race)	8m 7s
test (ubuntu-24.04, 1.23.x)	7m 14s
test (ubuntu-24.04, 1.23.x, criu-dev)	7m 54s
test (actuated-arm64-6cpu-8gb, 1.23.x, rootless)	11m 32s
test (actuated-arm64-6cpu-8gb, 1.23.x)	8m 12s
all-done	1s
	2h 44m 23s

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