Incorrect json round-trip with orient='table' when dataframe contains duplicate index values
#### Code Sample, a copy-pastable example if possible

```python
import pandas as pd
df = pd.DataFrame({"col1": [1, 2]}, index=[0, 0])
print(pd.read_json(df.to_json(orient='table'), orient='table'))
print(pd.read_json(df.to_json(orient='split'), orient='split'))
```
Output:
```python
   index  col1
0      0     1
1      0     2
   col1
0     1
0     2
```

#### Problem description

I would expect the json roundtrip to output a dataframe that is identical to the input, regardless of the value of the orient parameter.

#### Expected Output

```python
   col1
0     1
0     2
   col1
0     1
0     2
```

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

<details>

INSTALLED VERSIONS
------------------
commit           : None
python           : 3.7.4.final.0
python-bits      : 64
OS               : Linux
OS-release       : 4.15.0-50-generic
machine          : x86_64
processor        : x86_64
byteorder        : little
LC_ALL           : None
LANG             : en_US.UTF-8
LOCALE           : en_US.UTF-8

pandas           : 0.25.1
numpy            : 1.16.4
pytz             : 2019.3
dateutil         : 2.8.0
pip              : 19.1.1
setuptools       : 41.0.1
Cython           : None
pytest           : 5.0.1
hypothesis       : None
sphinx           : None
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : None
html5lib         : None
pymysql          : 0.9.3
psycopg2         : 2.8.3 (dt dec pq3 ext lo64)
jinja2           : 2.10.1
IPython          : 7.7.0
pandas_datareader: None
bs4              : None
bottleneck       : None
fastparquet      : None
gcsfs            : None
lxml.etree       : None
matplotlib       : 3.1.0
numexpr          : None
odfpy            : None
openpyxl         : None
pandas_gbq       : None
pyarrow          : None
pytables         : None
s3fs             : None
scipy            : 1.3.0
sqlalchemy       : 1.3.5
tables           : None
xarray           : None
xlrd             : None
xlwt             : None
xlsxwriter       : None
</details>
