I2CP: Fix error message for config errors (ticket #2639)

core/java/src/net/i2p/data/i2cp/SessionStatusMessage.java

@@ -34,6 +34,11 @@ public class SessionStatusMessage extends I2CPMessageImpl {
     public final static int STATUS_INVALID = 3;
     /** @since 0.9.12 */
     public final static int STATUS_REFUSED = 4;
+    /**
+     *  Used internally, not in spec, will be remapped to STATUS_INVALID before being sent.
+     *  @since 0.9.44
+     */
+    public final static int STATUS_DUP_DEST = 5;
 
     public SessionStatusMessage() {
         setStatus(STATUS_INVALID);