Fix importing unofficial TF models with extra optimizer weights
Author: monologg
Pull request: yes

Hi:)

I was trying to convert the BERT `tf model` to `torch model`, and tf model has *extra optimizer weights* ([This file](https://drive.google.com/file/d/1mNDA-SNCsnu60wzKVe_Y3k-dq3LoDHB2/view) is the one I've tried to convert).

But it encounters the error, and I've printed the parameters' name in tf model.

<img width="686" alt="Screen Shot 2020-01-27 at 10 21 50 PM" src="https://user-images.githubusercontent.com/28896432/73183937-f87e9d00-415e-11ea-9317-2611aecdefe7.png">

I've found out the instead of "adam_v" for "adam_m, names are saved as "AdamWeightDecayOptimizer" or "AdamWeightDecayOptimizer_1".

There was a similar issue that also encountered the issue that I had. ([Issue Link from DeepPavlov repo](https://github.com/deepmipt/DeepPavlov/issues/863))

I can't find out the exact reason why the parameters are named as "AdamWeightDecayOptimizer" or "AdamWeightDecayOptimizer_1" instead of "adam_v" or "adam_m", but it might be safe to cover all the exceptional cases:)

Comments:
# [Codecov](https://codecov.io/gh/huggingface/transformers/pull/2652?src=pr&el=h1) Report
> Merging [#2652](https://codecov.io/gh/huggingface/transformers/pull/2652?src=pr&el=desc) into [master](https://codecov.io/gh/huggingface/transformers/commit/babd41e7fa07bdd764f8fe91c33469046ab7dbd1?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `0%`.

[![Impacted file tree graph](https://codecov.io/gh/huggingface/transformers/pull/2652/graphs/tree.svg?width=650&token=9qOlN6Hb1c&height=150&src=pr)](https://codecov.io/gh/huggingface/transformers/pull/2652?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master    #2652   +/-   ##
=======================================
  Coverage   74.58%   74.58%           
=======================================
  Files          87       87           
  Lines       14892    14892           
=======================================
  Hits        11107    11107           
  Misses       3785     3785
```


| [Impacted Files](https://codecov.io/gh/huggingface/transformers/pull/2652?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [src/transformers/modeling\_bert.py](https://codecov.io/gh/huggingface/transformers/pull/2652/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ19iZXJ0LnB5) | `87.9% <0%> (ø)` | :arrow_up: |
| [src/transformers/modeling\_albert.py](https://codecov.io/gh/huggingface/transformers/pull/2652/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ19hbGJlcnQucHk=) | `79.14% <0%> (ø)` | :arrow_up: |
| [src/transformers/modeling\_t5.py](https://codecov.io/gh/huggingface/transformers/pull/2652/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ190NS5weQ==) | `81.09% <0%> (ø)` | :arrow_up: |

------

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> Powered by [Codecov](https://codecov.io/gh/huggingface/transformers/pull/2652?src=pr&el=footer). Last update [babd41e...d338eb0](https://codecov.io/gh/huggingface/transformers/pull/2652?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).