Fix build with current clang master

Compiling netd without the patch with current clang master errors out,
saying
cannot specify any part of a return type in the declaration of a conversion function; put the complete type after 'operator'

Change-Id: Ia49dd18f52982cf22b0aa8ade6b9a53ff24d26c0
Signed-off-by: Bernhard Rosenkränzer <Bernhard.Rosenkranzer@linaro.org>