de-virt Transport::getRevision()

Makes clear that this is/was only for TCP,
and eliminate redundant storage.  Also apply
locking to this storage.

Use header version directly in search handler.
Correct as only UDP search is actually used atm.

src/remoteClient/clientContextImpl.cpp

@@ -2784,8 +2784,6 @@ public:
     {
         AbstractClientResponseHandler::handleResponse(responseFrom, transport, version, command, payloadSize, payloadBuffer);
 
-        transport->setRemoteRevision(version);
-
         transport->ensureData(4+2);
 
         transport->setRemoteTransportReceiveBufferSize(payloadBuffer->getInt());