json_normalize errors if meta fields are integer
#### Code Sample, a copy-pastable example if possible

```python
import pandas as pd

data = [{"person_id": "test", 
         "test_field": 1,  
         "access": [{"step": 1, 
                     "phase":"starting"}, 
                    {"step":2,
                     "phase":"ending"}
                    ]
         }]

df = pd.json_normalize(data,"access",meta=["person_id","test_field"])

print(df)

```
#### Problem description
If meta fields are integer we get the below error. json_normalize works fine for string datatype
Traceback (most recent call last):
  File "C:/Users/HOME/PycharmProjects/pandas_test/pandas_test.py", line 12, in <module>
    df = pd.json_normalize(data,"access",meta=["person_id","test_field"])
  File "C:\Users\HOME\Anaconda3\envs\pandas_test\lib\site-packages\pandas\io\json\_normalize.py", line 327, in _json_normalize
    _recursive_extract(data, record_path, {}, level=0)
  File "C:\Users\HOME\Anaconda3\envs\pandas_test\lib\site-packages\pandas\io\json\_normalize.py", line 314, in _recursive_extract
    meta_val = _pull_field(obj, val[level:])
  File "C:\Users\HOME\Anaconda3\envs\pandas_test\lib\site-packages\pandas\io\json\_normalize.py", line 246, in _pull_field
    f"{js} has non iterable value {result} for path {spec}. "
TypeError: {'person_id': 'test', 'test_field': 1, 'access': [{'step': 1, 'phase': 'starting'}, {'step': 2, 'phase': 'ending'}]} has non iterable value 1 for path ['test_field']. Must be iterable or null.


#### Expected Output

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

<details>

INSTALLED VERSIONS
------------------
commit           : None
python           : 3.7.6.final.0
python-bits      : 64
OS               : Windows
OS-release       : 10
machine          : AMD64
processor        : AMD64 Family 16 Model 10 Stepping 0, AuthenticAMD
byteorder        : little
LC_ALL           : None
LANG             : None
LOCALE           : None.None

pandas           : 1.0.1
numpy            : 1.18.1
pytz             : 2019.3
dateutil         : 2.8.1
pip              : 20.0.2
setuptools       : 45.2.0.post20200210
Cython           : None
pytest           : None
hypothesis       : None
sphinx           : None
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : None
html5lib         : None
pymysql          : None
psycopg2         : None
jinja2           : None
IPython          : None
pandas_datareader: None
bs4              : None
bottleneck       : None
fastparquet      : None
gcsfs            : None
lxml.etree       : None
matplotlib       : None
numexpr          : None
odfpy            : None
openpyxl         : None
pandas_gbq       : None
pyarrow          : None
pytables         : None
pytest           : None
pyxlsb           : None
s3fs             : None
scipy            : None
sqlalchemy       : None
tables           : None
tabulate         : None
xarray           : None
xlrd             : None
xlwt             : None
xlsxwriter       : None
numba            : None

</details>
