Fix for #2869 overlapping windows. Source was emitting t multiple times while holding queue.

Author: Alex Wenckus

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

@@ -119,7 +119,7 @@ public void onNext(T t) {
                 do {
                     drain(localQueue);
                     if (once) {
-                        once = true;
+                        once = false;
                         emitValue(t);
                     }