Hello, guys.

I'm using the netconf testtool to test a NETCONF device manager, and one of the tests is to check how the manager would handle a (relatively) large configuration data received through a get-config request.

For that, I'm using a dummy config file 27MB large and passing it in command line with the --initial-config-xml-file parameter. The entire command I used for running the application is this:

```
java -jar netconf-testtool-5.0.6-executable.jar --schemas-dir yang_modules --initial-config-xml-file get_config_response.xml --starting-port 17900 --ip 127.0.0.1

```

The memory consumption when the application starts is around 120MB. Using a NETCONF client and sending a get-config request, the consumption goes to 750MB; when a second get-config is sent, the consumption goes to 1.1GB and stays at that level for ever if you don't interact with it anymore.

Could you please have a look at this?
I reproduced the same issue with version 3.0.9.

Attached are the config data file I'm using and a log file. I tried to upload a heap dump I collected but its size exceeds the limit.