Fix valgrind errors for simple-wifi-frame-aggregation example.

src/devices/wifi/msdu-standard-aggregator.cc

@@ -64,7 +64,8 @@ MsduStandardAggregator::Aggregate (Ptr<const Packet> packet, Ptr<Packet> aggrega
     {
       if (padding)
         {
-          aggregatedPacket->AddPaddingAtEnd (padding);
+          Ptr<Packet> pad = Create<Packet> (padding);
+          aggregatedPacket->AddAtEnd (pad);
         }
       currentHdr.SetDestinationAddr (dest);
       currentHdr.SetSourceAddr (src);

src/internet-stack/icmpv6-l4-protocol.cc

@@ -962,7 +962,7 @@ void Icmpv6L4Protocol::SendRedirection (Ptr<Packet> redirectedPacket, Ipv6Addres
 
   if ((redirectedPacketSize % 8) != 0)
   {
-    Ptr<Packet> pad = Create<Packet>(8 - (redirectedPacketSize % 8));
+    Ptr<Packet> pad = Create<Packet> (8 - (redirectedPacketSize % 8));
     redirectedPacket->AddAtEnd (pad); 
   }