message: CMake: configure default string values of options properly
  Because cmake configures defaults values as ON or OFF only,
  string values as default doesn't work.
  Thus, when it is set "OFF", we need to re-set the values.
  Fixes
diff: @@ -53,7 +53,15 @@ if (NOT WIN32)
  set(tensorflow_CUDNN_INCLUDE /usr/include)
  endif (NOT tensorflow_CUDNN_INCLUDE)
  option(tensorflow_PATH_CUDNN_STATIC_LIB "Override PATH_STATIC_LIB for libcudnn_static.a" ${tensorflow_PATH_STATIC_LIB})
  + if (NOT tensorflow_PATH_CUDNN_STATIC_LIB)
  + # option's default value is OFF. Fill it with real default values
  + set (tensorflow_PATH_CUDNN_STATIC_LIB ${tensorflow_PATH_STATIC_LIB})
  + endif (NOT tensorflow_PATH_CUDNN_STATIC_LIB)
  option(tensorflow_PATH_NCCL_STATIC_LIB "Override PATH_STATIC_LIB for libnccl_static.a" ${tensorflow_PATH_STATIC_LIB})
  + if (NOT tensorflow_PATH_NCCL_STATIC_LIB)
  + # option's default value is OFF. Fill it with real default values
  + set (tensorflow_PATH_NCCL_STATIC_LIB ${tensorflow_PATH_STATIC_LIB})
  + endif (NOT tensorflow_PATH_NCCL_STATIC_LIB)
  option(tensorflow_CUDA_LIBRARY_PATH "Designate the default CUDA library paths" /usr/local/cuda/lib64)
  if (NOT tensorflow_CUDA_LIBRARY_PATH)
  # option's default value is OFF. Fill it with real default values
  