Unconditionally call nvidia-modprobe to load UVM
Unconditionally call nvidia-modprobe to load UVM

Checking the existence of /dev/nvidia-uvm had two limitations:
- If kernel module nvidia_uvm is unloaded, /dev/nvidia-uvm is not
  removed, so nvidia-modprobe was not called when it should have.
- Even if kernel module nvidia_uvm is loaded and /dev/nvidia-uvm
  exists, /dev/nvidia-uvm-tools might not exist. Using nvidia-modprobe
  fixes this issue.

nvidia-modprobe parses /proc/modules to check which modules are
already loaded, so there should be no impact on performance.

NVIDIA/nvidia-docker