wifi: Replace platform specific std::path::c_str() with std::path::string()
Window's std::path::c_str() returns wchar* instead o char*
Fixes #1082 (closed) for Windows.
The MacOS test failure, based on what Tom and Stefano said, could be just collisions lowering the expected throughput and causing the test to fail after the recent changes.
Edited by Gabriel Ferreira