Cherrypick the change for setRPort() in Via header.

Change-Id: I3bd1acb75a09430d1618e4978441052e51092d40
diff --git a/java/gov/nist/javax/sip/header/Via.java b/java/gov/nist/javax/sip/header/Via.java
index 2253394..be40962 100644
--- a/java/gov/nist/javax/sip/header/Via.java
+++ b/java/gov/nist/javax/sip/header/Via.java
@@ -96,6 +96,8 @@
      */
     protected String comment;
 
+    private boolean rPortFlag = false;
+
     /** Default constructor
     */
     public Via() {
@@ -265,6 +267,7 @@
         if (comment != null) {
             buffer.append(SP).append(LPAREN).append(comment).append(RPAREN);
         }
+        if (rPortFlag) buffer.append(";rport");
         return buffer;
     }
 
@@ -324,11 +327,7 @@
      * Set the RPort flag parameter
      */
     public void setRPort(){
-        try {
-            this.setParameter(Via.RPORT,"");
-        } catch (ParseException e) {
-            e.printStackTrace();    // should not occur
-        }
+        rPortFlag = true;
     }
 
     /**