invoking pivot_table results in unwanted row
#### I have encounterd an issue with pd.pivot_table. this function adds unexpected row and I have no idea to remove it.
below is the code:
```python
import pandas as pd
import numpy as np

dates = {
    'animal': ['cat', 'cat', 'wolf'],
    'color': ['white', 'black', 'black'],
    'age': np.random.randint(15, 30, 3)}

df = pd.DataFrame(dates)
dfp = pd.pivot_table(
    df,
    index='animal',
    columns='color',
    values='age',
    aggfunc=[len, np.mean],
    fill_value=0
)

excel_file = pd.ExcelWriter('result.xlsx', mode='w')

dfp.to_excel(
    excel_writer=excel_file,
    sheet_name='before'
)
```
### the result is:

  | len |　 | mean|　 
-- | -- |-- |-- |--
color | black | white | black | white
animal |   |   |   |  
cat | 1 | 1 | 20 | 28
wolf | 1 | 0 | 24 | 0

#### Problem description
pivot_table adds unwanted row below the MultiIndex. this row starts with 'animal' which is the index name.
I have read though related docs and tried possible parameters.
Finallly I found there is no way to remove it.

#### Expected Output

  | len | 　 | mean |　　
-- | -- | -- | -- | --
color | black | white | black | white
cat | 1 | 1 | 20 | 28
wolf | 1 | 0 | 24 | 0


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

<details>

[paste the output of ``pd.show_versions()`` here below this line]
INSTALLED VERSIONS
------------------
commit           : None
python           : 3.7.4.final.0
python-bits      : 64
OS               : Windows
OS-release       : 10
machine          : AMD64
processor        : Intel64 Family 6 Model 142 Stepping 10, GenuineIntel
byteorder        : little
LC_ALL           : None
LANG             : None
LOCALE           : None.None

pandas           : 0.25.0
numpy            : 1.17.0
pytz             : 2019.2
dateutil         : 2.8.0
pip              : 19.2.1
setuptools       : 41.0.1
Cython           : None
pytest           : None
hypothesis       : None
sphinx           : None
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : None
html5lib         : None
pymysql          : None
psycopg2         : None
jinja2           : 2.10.1
IPython          : None
pandas_datareader: None
bs4              : None
bottleneck       : None
fastparquet      : None
gcsfs            : None
lxml.etree       : None
matplotlib       : 3.1.1
numexpr          : 2.6.9
odfpy            : None
openpyxl         : 2.6.2
pandas_gbq       : None
pyarrow          : None
pytables         : None
s3fs             : None
scipy            : 1.3.0
sqlalchemy       : None
tables           : None
xarray           : None
xlrd             : 1.2.0
xlwt             : 1.3.0
xlsxwriter       : None

</details>
