<include> with ros_pkg does not work anymore with ROS 1 (in BehaviorTree.CPP version 3.8)

[divbyzerofordummies]

Version BehaviorTree.CPP: 3.8

In xml_parsing.cpp, void XMLParser::Pimpl::loadDocImpl, the #ifdef clauses are incorrect since for USING_ROS, the variable ros_pkg_path is not used to update the file_path.

The include of other XML files is therefore performed relative to the current path and not the ROS package path.