BUG: Unable to write to hdf when format='table' and list-like values are present in a column
- [x] I have checked that this issue has not already been reported.

- [x] I have confirmed this bug exists on the latest version of pandas.

- [ ] (optional) I have confirmed this bug exists on the master branch of pandas.

---



#### Code Sample, a copy-pastable example

```python
In[43]: df = pd.DataFrame({'a':[[1, 2, 3]]})
In[44]: df
Out[44]: 
           a
0  [1, 2, 3]
In[45]: df.to_hdf('sample.hdf', 'test')
/home/pgali/anaconda3/envs/cudf_dev/lib/python3.7/site-packages/pandas/core/generic.py:2449: PerformanceWarning: 
your performance may suffer as PyTables will pickle object types that it cannot
map directly to c-types [inferred_type->mixed,key->block0_values] [items->Index(['a'], dtype='object')]

  encoding=encoding,
In[46]: df.to_hdf('sample.hdf', 'test')
/home/pgali/anaconda3/envs/cudf_dev/lib/python3.7/site-packages/pandas/core/generic.py:2449: PerformanceWarning: 
your performance may suffer as PyTables will pickle object types that it cannot
map directly to c-types [inferred_type->mixed,key->block0_values] [items->Index(['a'], dtype='object')]

  encoding=encoding,
In[47]: df.to_hdf('sample.hdf', 'test', format='table')
Traceback (most recent call last):
  File "/home/pgali/anaconda3/envs/cudf_dev/lib/python3.7/site-packages/IPython/core/interactiveshell.py", line 3418, in run_code
    exec(code_obj, self.user_global_ns, self.user_ns)
  File "<ipython-input-47-13d7ad5be031>", line 1, in <module>
    df.to_hdf('sample.hdf', 'test', format='table')
  File "/home/pgali/anaconda3/envs/cudf_dev/lib/python3.7/site-packages/pandas/core/generic.py", line 2449, in to_hdf
    encoding=encoding,
  File "/home/pgali/anaconda3/envs/cudf_dev/lib/python3.7/site-packages/pandas/io/pytables.py", line 270, in to_hdf
    f(store)
  File "/home/pgali/anaconda3/envs/cudf_dev/lib/python3.7/site-packages/pandas/io/pytables.py", line 262, in <lambda>
    encoding=encoding,
  File "/home/pgali/anaconda3/envs/cudf_dev/lib/python3.7/site-packages/pandas/io/pytables.py", line 1129, in put
    track_times=track_times,
  File "/home/pgali/anaconda3/envs/cudf_dev/lib/python3.7/site-packages/pandas/io/pytables.py", line 1801, in _write_to_group
    track_times=track_times,
  File "/home/pgali/anaconda3/envs/cudf_dev/lib/python3.7/site-packages/pandas/io/pytables.py", line 4238, in write
    data_columns=data_columns,
  File "/home/pgali/anaconda3/envs/cudf_dev/lib/python3.7/site-packages/pandas/io/pytables.py", line 3907, in _create_axes
    errors=self.errors,
  File "/home/pgali/anaconda3/envs/cudf_dev/lib/python3.7/site-packages/pandas/io/pytables.py", line 4896, in _maybe_convert_for_string_atom
    for i in range(len(block.shape[0])):
TypeError: object of type 'int' has no len()

```

#### Problem description

My dataframe has list-like values and when we pass `format=table`, I'm not able to write the dataframe to hdf.

#### Expected Output

#### Output of ``pd.show_versions()``

<details>

INSTALLED VERSIONS
------------------
commit           : b5958ee1999e9aead1938c0bba2b674378807b3d
python           : 3.7.9.final.0
python-bits      : 64
OS               : Linux
OS-release       : 5.8.0-36-generic
Version          : #40~20.04.1-Ubuntu SMP Wed Jan 6 10:15:55 UTC 2021
machine          : x86_64
processor        : x86_64
byteorder        : little
LC_ALL           : None
LANG             : en_US.UTF-8
LOCALE           : en_US.UTF-8
pandas           : 1.1.5
numpy            : 1.19.5
pytz             : 2020.5
dateutil         : 2.8.1
pip              : 20.3.3
setuptools       : 49.6.0.post20210108
Cython           : 0.29.21
pytest           : 6.2.1
hypothesis       : 6.0.0
sphinx           : 3.4.3
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : None
html5lib         : None
pymysql          : None
psycopg2         : None
jinja2           : 2.11.2
IPython          : 7.19.0
pandas_datareader: None
bs4              : None
bottleneck       : None
fsspec           : 0.8.5
fastparquet      : None
gcsfs            : None
matplotlib       : None
numexpr          : 2.7.2
odfpy            : None
openpyxl         : None
pandas_gbq       : None
pyarrow          : 1.0.1
pytables         : None
pyxlsb           : None
s3fs             : None
scipy            : None
sqlalchemy       : None
tables           : 3.6.1
tabulate         : None
xarray           : None
xlrd             : None
xlwt             : None
numba            : 0.52.0

</details>
