OperatorScan should check for MAX_VALUE on request

Author: davidmoten

src/main/java/rx/internal/operators/OperatorScan.java

@@ -129,7 +129,7 @@ public void setProducer(final Producer producer) {
                     @Override
                     public void request(long n) {
                         if (once.compareAndSet(false, true)) {
-                            if (initialValue == NO_INITIAL_VALUE) {
+                            if (initialValue == NO_INITIAL_VALUE || n == Long.MAX_VALUE) {
                                 producer.request(n);
                             } else {
                                 producer.request(n - 1);