message: Move blasLt SetBiasPointer call inside mutex lock
  This was not thread-safe before.
diff: @@ -3493,13 +3493,6 @@ bool CUDABlas::DoBlasLtMatmulInternal(
  "epilogue for the given bias pointer.";
  return false;
  }
  - if (bias != nullptr) {
  - if (!cuda_plan.SetBiasPointer(bias.opaque())) {
  - VLOG(2) << "DoBlasLtMatmul returning false because setting the bias "
  - "pointer failed.";
  - return false;
  - }
  - }
  const void *alpha_ptr = alpha.is_pointer() ? alpha.opaque_pointer().opaque()
  : alpha.opaque_value();
  const void *beta_ptr =
  @@ -3524,6 +3517,14 @@ bool CUDABlas::DoBlasLtMatmulInternal(
  absl::MutexLock lock(&mu_);
  + if (bias != nullptr) {
  + if (!cuda_plan.SetBiasPointer(bias.opaque())) {
  + VLOG(2) << "DoBlasLtMatmul returning false because setting the bias "
  + "pointer failed.";
  + return false;
  + }
  + }
  +
  CHECK(blasLt_ != nullptr);
  gpu::ScopedActivateExecutorContext sac{parent_};
  