Enable limits options in CcnxStackHelper

Slightly modifying the way of how forwarding strategy is hooked up
diff --git a/model/ccnx-face.h b/model/ccnx-face.h
index 397a5b0..94b48ab 100644
--- a/model/ccnx-face.h
+++ b/model/ccnx-face.h
@@ -169,6 +169,12 @@
   SetBucketMax (double bucket);
 
   /**
+   * @brief Set a normalized value (one second) for Interest allowance bucket leak
+   */
+  inline void
+  SetBucketLeak (double leak);
+  
+  /**
    * @brief Leak the Interest allowance bucket by (1/interval) * m_bucketMax amount
    *
    * @param interval Time interval with which the bucket is leaked
@@ -249,6 +255,12 @@
 }
 
 void
+CcnxFace::SetBucketLeak (double leak)
+{
+  m_bucketLeak = leak;
+}
+
+void
 CcnxFace::LeakBucket (const Time &interval)
 {
   const double leak = m_bucketLeak * 1.0 / interval.ToDouble (Time::S);