Use a blank default for the library path since we are actually using it now.

theano/configdefaults.py

@@ -345,25 +345,16 @@ def default_dnn_include_path():
     return os.path.join(cuda_root, 'include')
 
 
-def default_dnn_library_path():
-    cuda_root = get_cuda_root()
-    if cuda_root == '':
-        return ''
-    if sys.platform == 'darwin':
-        return os.path.join(cuda_root, 'lib')
-    if sys.platform == 'win32':
-        return os.path.join(cuda_root, 'lib', 'x64')
-    return os.path.join(cuda_root, 'lib64')
-
 AddConfigVar('dnn.include_path',
              "Location of the cudnn header (defaults to the cuda root)",
+             # We keep the default here since cudnn needs headers from cuda
              StrParam(default_dnn_include_path()),
              # Added elsewhere in the c key only when needed.
              in_c_key=False)
 
 AddConfigVar('dnn.library_path',
              "Location of the cudnn library (defaults to the cuda root)",
-             StrParam(default_dnn_library_path()),
+             StrParam(''),
              # Added elsewhere in the c key only when needed.
              in_c_key=False)