pandas.DataFrame.applymap run not expected
#### Code Sample, a copy-pastable example if possible

```python
>>> import numpy as np
>>> import pandas as pd
>>> df = pd.DataFrame([[1, 2.12], [3.356, 4.567]])
>>> df
       0      1
0  1.000  2.120
1  3.356  4.567
>>> def test(x):
...     print(x)
...
>>> df.applymap(lambda x: test(x))
1.0
3.356
1.0
3.356
2.12
4.567

```
#### Problem description

Hello, I run pandas.DataFrame.applymap, and it seems that **this function call twice on the first columns**. Is it a bug?

#### Expected Output

```python
1.0
3.356
2.12
4.567
```
#### Output of ``pd.show_versions()``

<details>

[paste the output of ``pd.show_versions()`` here below this line]

INSTALLED VERSIONS
------------------
commit: None
python: 3.6.6.final.0
python-bits: 64
OS: Windows
OS-release: 10
machine: AMD64
processor: Intel64 Family 6 Model 60 Stepping 3, GenuineIntel
byteorder: little
LC_ALL: None
LANG: None
LOCALE: None.None

pandas: 0.23.4
pytest: None
pip: 10.0.1
setuptools: 39.0.1
Cython: None
numpy: 1.15.4
scipy: 1.2.0
pyarrow: 0.11.1
xarray: None
IPython: 7.2.0
sphinx: None
patsy: None
dateutil: 2.7.5
pytz: 2018.7
blosc: None
bottleneck: None
tables: None
numexpr: None
feather: None
matplotlib: 3.0.2
openpyxl: 2.5.12
xlrd: 1.2.0
xlwt: 1.3.0
xlsxwriter: None
lxml: 4.2.5
bs4: 4.7.1
html5lib: None
sqlalchemy: 1.3.1
pymysql: None
psycopg2: None
jinja2: 2.10
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None

</details>
