simplify clean-up of space stage #2723

Job	Run time
build	10m 32s
test_when_cache_missing	0s
test_when_cache_present (0, 11, 675)	37m 10s
test_when_cache_present (1, 11, 675)	29m 30s
test_when_cache_present (2, 11, 675)	33m 5s
test_when_cache_present (3, 11, 675)	37m 30s
test_when_cache_present (4, 11, 675)	30m 48s
test_when_cache_present (5, 11, 675)	29m 16s
test_when_cache_present (6, 11, 675)	36m 34s
test_when_cache_present (7, 11, 675)	29m 59s
test_when_cache_present (8, 11, 675)	28m 55s
test_when_cache_present (9, 11, 675)	32m 44s
test_when_cache_present (10, 11, 675)	39m 23s
test_when_cache_present (11, 11, 675)	22m 21s
save_test_times_when_cache_missing	0s
save_test_times_when_cache_present	7s
	6h 37m 54s

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