Simplify snapshot compress/decompress logic #2981

Job	Run time
build / Build	7m 44s
build-windows / Build	7m 44s
Integration Tests (windows)	1m 38s
Integration Tests (etcdrestore)	4m 26s
Integration Tests (longhorn)	5m 41s
Integration Tests (secretsencryption)	4m 59s
Integration Tests (startup)	12m 29s
Integration Tests (certrotation)	4m 34s
Integration Tests (cacertrotation)	5m 42s
Integration Tests (custometcdargs)	4m 47s
Integration Tests (flannelnone)	3m 59s
Integration Tests (kubeflags)	9m 11s
Integration Tests (etcdsnapshot)	12m 22s
Integration Tests (localstorage)	4m 0s
	1h 29m 16s

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