Pass stats interval colleciton to executor

This fixes a bug where executor based drivers emit stats every second,
regardless of user configuration.

When serializing the Stats request across grpc, the nomad agent dropped
the Interval value, and then executor uses 1s as a default value.

drivers/shared/executor/client.go

@@ -107,7 +107,9 @@ func (c *grpcExecutorClient) Version() (*ExecutorVersion, error) {
 }
 
 func (c *grpcExecutorClient) Stats(ctx context.Context, interval time.Duration) (<-chan *cstructs.TaskResourceUsage, error) {
-	stream, err := c.client.Stats(ctx, &proto.StatsRequest{})
+	stream, err := c.client.Stats(ctx, &proto.StatsRequest{
+		Interval: int64(interval),
+	})
 	if err != nil {
 		return nil, err
 	}