[dock] Use --runtime for nvidia enabled container

The nvidia-docker2 package recommends to use the --runtime
parameter to select the nvidia runtime when using a GPU
enabled container with CUDA.

beat/core/dock.py

@@ -337,7 +337,7 @@ class Host(object):
         if container.image in Host.images_cache:
             image_infos = Host.images_cache[container.image]
             if ('capabilities' in image_infos) and ('gpu' in image_infos['capabilities']):
-                cmd[0] = 'nvidia-docker'
+                cmd.append('--runtime=nvidia')
 
 
         if virtual_memory_in_megabytes: