---- Set the m_traceFilePath to a deafult value, to fix valgrind error saying that the value has not been initialized. user: Mohamed Amine Ismail <amine.ismail at sophia.inria.fr> files: src/devices/wimax/snr-to-block-error-rate-manager.cc url: http://code.nsnam.org/iamine/ns-3-wimax/rev/323bfbcdd184