Don't use both of them. Both are of completely different GPU generations and completely different GPU architectures! Your GTX 1080 is of a much newer GPU architecture than that Tesla K10. What's more, Tesla cards do NOT support GeForces as the primary GPU. Only a Quadro K series GPU is supported by that Tesla K10. If you try to use that Tesla K10 in your system, the card either will not work at all or will cause major stability issues in your system.
Users with both integrated Intel HD, UHD or Iris graphics and an AMD GPU will face EXACTLY the same problem as you will. In this case, when OpenCL or (OSX only) Metal is selected, then only the Intel graphics (or whichever GPU is set to primary) will be used at all for GPU acceleration, ignoring the other GPU completely.
So if you MUST use two CUDA GPUs, both of them MUST be of exactly the same GPU generation AND the same GPU architecture.