Fix DebugHookTest as per direction from @abersnaze

Author: benjchristensen

src/test/java/rx/debug/DebugHookTest.java

@@ -63,7 +63,7 @@ public void onError(Throwable e) {
             public void onNext(Integer t) {
             }
         });
-        verify(events, times(6)).call(subscribe());
+        verify(events, atLeast(3)).call(subscribe());
         verify(events, times(4)).call(onNext(1));
         // one less because it originates from the inner observable sent to merge
         verify(events, times(3)).call(onNext(2));