Fix CircleCI IVFPQ GPU tests (#1690)
Fix CircleCI IVFPQ GPU tests (#1690)

Summary:
Pull Request resolved: https://github.com/facebookresearch/faiss/pull/1690

The GPU and CPU were trained separately in the failing test, leading to fairly different PQ centroids. Instead, just train on the GPU and copy to the CPU like other tests.

Also silences the not enough centroids warnings.

Reviewed By: beauby

Differential Revision: D26470199

fbshipit-source-id: 1f7c036671c03ed4a97c8c4a44d3c5b9767019cb

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