message: Enable int8 support for FloorDiv
  int8 is enabled for FloorDiv in math_ops.cc though
  the kernel was not registered.
  This fix register the int8 kernel for FloorDiv, and enables
  the test case for it.
diff: @@ -16,8 +16,8 @@ limitations under the License.
  #include "tensorflow/core/kernels/cwise_ops_common.h"
  namespace tensorflow {
  -REGISTER5(BinaryOp, CPU, "FloorDiv", functor::safe_floor_div, uint8, uint16,
  - int16, int32, int64);
  +REGISTER6(BinaryOp, CPU, "FloorDiv", functor::safe_floor_div, uint8, uint16,
  + int8, int16, int32, int64);
  REGISTER3(BinaryOp, CPU, "FloorDiv", functor::floor_div_real, float,
  Eigen::half, double);
  