Mask RCNN serving containers have default number of server workers equal to #cpu

The default number of server workers for Mask RCNN serving containers is set to number of CPUs, which is typically very high on P3 GPU machines. The default setting should be 1, as an environment variable allows it to be changed.

Locate the Mask RCNN serving-container configuration in the repository and find where the default server-worker count is derived. Confirm that the default is set to 1 while the documented environment-variable override remains available, then verify the serving example or container starts with that default.

Written by the indexing model from the issue text.