Implement ActivationClientProxy

ActivationClientProxy actor fetches activationMessage from scheudler side
using akka grpc, and forwards the activationMessage to its parent actor
FunctionPullContainerProxy actor.

Author: ningyougang

common/scala/src/main/scala/org/apache/openwhisk/common/TransactionId.scala

@@ -191,6 +191,8 @@ case class TransactionId private (meta: TransactionMetadata) extends AnyVal {
       case Some(parent) => findRoot(parent)
       case _            => meta
     }
+
+  def serialize = TransactionId.serdes.write(this).compactPrint
 }
 
 /**