tests: enable previously skipped tests #2051

Job	Run time
prepare	1s
test / prepare	1m 46s
test / run (containerd, ./frontend/dockerfile, integration)	4m 40s
test / run (containerd, ./frontend/dockerfile, dockerfile)	6m 7s
test / run (containerd-rootless, ./frontend/dockerfile, integration)	4m 22s
test / run (containerd-rootless, ./frontend/dockerfile, dockerfile)	5m 36s
test / run (containerd-1.6, ./frontend/dockerfile, integration)	4m 8s
test / run (containerd-1.6, ./frontend/dockerfile, dockerfile)	6m 3s
test / run (containerd-snapshotter-stargz, ./frontend/dockerfile, integration)	4m 18s
test / run (containerd-snapshotter-stargz, ./frontend/dockerfile, dockerfile)	7m 8s
test / run (oci, ./frontend/dockerfile, integration)	3m 55s
test / run (oci, ./frontend/dockerfile, dockerfile)	5m 29s
test / run (oci-rootless, ./frontend/dockerfile, integration)	4m 16s
test / run (oci-rootless, ./frontend/dockerfile, dockerfile)	5m 21s
test / run (oci-snapshotter-stargz, ./frontend/dockerfile, integration)	4m 23s
test / run (oci-snapshotter-stargz, ./frontend/dockerfile, dockerfile)	5m 7s
image (mainline)	4m 57s
image (labs)	4m 35s
release	0s
	1h 22m 12s

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