Need to delete snapshot before deleting volume

[wnxn]

Hi,
It is better to delete snapshot before deleting volume at cleaning up stage of ListSnapshots testcase. So, we could change the cleaner:

csi-test/pkg/sanity/controller.go

Lines 1208 to 1216 in 3e3231b

	By("cleaning up deleting the volume")
	delVolReq := MakeDeleteVolumeReq(sc, volume.GetVolume().GetId())
	_, err = c.DeleteVolume(context.Background(), delVolReq)
	Expect(err).NotTo(HaveOccurred())
	By("cleaning up deleting the snapshot")
	delSnapReq := MakeDeleteSnapshotReq(sc, snapshot.GetSnapshot().GetId())
	_, err = c.DeleteSnapshot(context.Background(), delSnapReq)
	Expect(err).NotTo(HaveOccurred())

to：

csi-test/pkg/sanity/controller.go

Lines 1251 to 1259 in 3e3231b

	By("cleaning up deleting the snapshot")
	delSnapReq := MakeDeleteSnapshotReq(sc, snapshot.GetSnapshot().GetId())
	_, err = c.DeleteSnapshot(context.Background(), delSnapReq)
	Expect(err).NotTo(HaveOccurred())
	By("cleaning up deleting the volume")
	delVolReq := MakeDeleteVolumeReq(sc, volume.GetVolume().GetId())
	_, err = c.DeleteVolume(context.Background(), delVolReq)
	Expect(err).NotTo(HaveOccurred())