Fix functionality of the test tool

The testool under netconf/tools/netconf-testtool consists of multiple parts
which need to be updated.

1. netconf-testool
The automatic bulk registration of devices on the controller via RESTCONF is broken.
The tool also uses old draft-bierman-netconf-restconf-02 paths - we would like to update to RFC 8040 paths.

2. rest-perf-client
The tool is using old draft-bierman-netconf-restconf-02 paths.
To update to RFC 8040 the tool is missing proper authorization of requests.

3. scale-util
The tool has multiple issues. It cannot correctly stop and start Karaf container.
In addition it is still using draft-bierman-netconf-restconf-02 noauth feature.
To update to RFC 8040 feature a proper authorization needs to be implemented in the tool.

4. stress-client
This tool is working with NETCONF protocol and works as expected.

In general the code of all tools can/should be refactored because it contains a lot
of duplicate logic.