[caffe2] Fix DBFileReader (#53498)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/53498
This code depended on `Blobs()` being returned in sorted order:
https://www.internalfb.com/intern/diffusion/FBS/browsefile/master/fbcode/caffe2/caffe2/python/db_file_reader.py?commit=472774e7f507e124392491800d9654e01269cbaf&lines=89-91
But D26504408 (https://github.com/pytorch/pytorch/commit/69bb0e028596d481cda38a0f49bcb5965fab4293) changed the underlying storage to a hashmap, so now the blobs are returned in arbitrary order (Note that `Blobs()` returns also non-local blobs, and for those there was already no guarantee of ordering).
So we need to explicitly sort the result.
Test Plan:
```
$ buck test dper3/dper3/toolkit/tests:lime_test
$ buck test //dper3/dper3/toolkit/tests:model_insight_test
```
Pass after this diff.
Differential Revision: D26879502
fbshipit-source-id: d76113f8780544af1d97ec0a818fb21cc767f2bf
