ListSnapshots test makes invalid assumption about NextToken

[bswartz]

https://github.com/kubernetes-csi/csi-test/blob/master/pkg/sanity/controller.go#L1352
says
Expect(nextToken).To(Equal(strconv.Itoa(maxEntries)))

The ListSnapshots tests assumes that the NextToken field of the ListSnapshotsResponse message is a string representation of an integer. It also assumes that integer is equal to MaxEntries. The CSI spec says neither of these things, so this is a bad test.

According to the CSI spec, NextToken is merely an opaque string that should be passed back to another invocation of ListSnapshots, so a better test would be to call ListSnapshots with the returned token and validate that the first page of snapshots plus the second page of snapshots equals the whole list of unpaginated snapshots.

At a minimum we need to remove the bad line from the test because it encourages CSI driver authors to implement snapshot list pagination in a dumb way.