Revert D26617038: [caffe2] use AddNAlreadyReserved() when serializing blobs
Test Plan: revert-hammer
Differential Revision:
D26617038 (https://github.com/pytorch/pytorch/commit/b4a8d98247c4eac60ae594ae626886408dc4e2c0)
Original commit changeset: 97dedbae889d
fbshipit-source-id: 6921d0a64dee26e18f16628773953bbe7280998e
