CSI: fix timestamp from volume snapshot responses (#12352)

Listing snapshots was incorrectly returning nanoseconds instead of
seconds, and formatting of timestamps both list and create snapshot
was treating the timestamp as though it were nanoseconds instead of
seconds. This resulted in create timestamps always being displayed as
zero values.

Fix the unit conversion error in the command line and the incorrect
extraction in the CSI plugin client code. Beef up the unit tests to
make sure this code is actually exercised.

command/volume_snapshot_list.go

@@ -186,7 +186,7 @@ func csiFormatSnapshots(snapshots []*api.CSISnapshot, verbose bool) string {
 			v.ID,
 			limit(v.ExternalSourceVolumeID, length),
 			humanize.IBytes(uint64(v.SizeBytes)),
-			formatUnixNanoTime(v.CreateTime),
+			formatUnixNanoTime(v.CreateTime*1e9), // seconds to nanoseconds
 			v.IsReady,
 		))
 	}