Added volatile to ServiceFuture's valueSet flag, so in case isCancelled gets called from a thread other than the subscribe thread the calling thread sees the value change.

Author: vcolin7

client-runtime/src/main/java/com/microsoft/rest/ServiceFuture.java

@@ -25,7 +25,7 @@ public class ServiceFuture<T> extends AbstractFuture<T> {
      * The Retrofit method invocation.
      */
     private Subscription subscription;
-    private boolean valueSet = false;
+    private volatile boolean valueSet = false;
 
     protected ServiceFuture() {
     }