Multiple CUDA contexts with digits-server

[lukeyeager]

To reproduce:

1. Turn off device_query caching
   • Change the default value for force_reload to True here
2. Run digits-server

   • After Add some more error checking in device_query #844, you should see this error in the server output:

     ...
     cudaGetDeviceProperties() failed with error #3
     ...
     return get_devices()[int(device_id)]
     IndexError: list index out of range
     ...
     

gunicorn does a fork of the DIGITS server, and the server creates a CUDA context in the parent before forking. Then, when the child tries to call cudaGetDevicesProperties(), it fails with an initialization error. We need to make sure we don't make any CUDA calls in the DIGITS server before forking when running with gunicorn, if possible.

[lukeyeager]

No longer an issue because gunicorn was removed with #1127.