feat: disallow usage of GPUs to CPU-only jobs (#96)

In Nomad jobs that didn't requested GPU, if the job landed in a GPU node and the job's docker image had CUDA libraries installed, then the job could access **all** the GPU of the node. Even if it didn't request any.

So for CPU-only jobs we set `NVIDIA_VISIBLE_DEVICES` to `None` to hide GPUs.

We also checked that jobs that asked one GPU got indeed only one GPU in the node (Nomad works fine in this case).

Author: Sftobias

ai4papi/routers/v1/deployments/modules.py

@@ -283,6 +283,7 @@ def create_deployment(
     # Modify the GPU section
     if user_conf["hardware"]["gpu_num"] <= 0:
         # Delete GPU section in CPU deployments
+        usertask["Env"]["NVIDIA_VISIBLE_DEVICES"] = "none"
         usertask["Resources"]["Devices"] = None
     else:
         # If gpu_type not provided, remove constraint to GPU model