loader: `Remove the ICD and Layers search path for Windows

This makes it more like Linux which leaves it up to the system
LoadLibrary() call to find the .dll as specified in the .json files.
Hard-coding "C:" or any other search path creates the possibility of
picking up the wrong .dll. The LoadLibrary() implementation does the
right thing.

Change-Id: I58cbdf230a1e86481067efb4aec03447ee55f1ff