crosstab sometimes erroneously handles dt operations
#### Code Sample

```python
import pandas as pd
df = pd.DataFrame({'date': ['2019-01-01', '2019-02-01', '2018-01-01', '2018-02-01']})
df["date"] = pd.to_datetime(df["date"])
pd.crosstab(df["date"].dt.month, df["date"].dt.year)
```
#### Problem description

This gives my a `2x2` table with the years 2018 and 2019 on both axes, thus wrongly treating the `dt.month` operation. The same thing happens if I replace `dt.month` with `dt.day` in my example. Interestingly, `pd.crosstab(df["date"].dt.day, df["date"].dt.month)` works as expected, while `pd.crosstab(df["date"].dt.month, df["date"].dt.day)` does not!

#### Expected Output
| year  | 2018 | 2019 |
|-------|------|------|
| month |      |      |
| 1     | 1    | 1    |
| 2     | 1    | 1    |
#### Output of ``pd.show_versions()``

<details>

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 78 Stepping 3, GenuineIntel
byteorder        : little
LC_ALL           : None
LANG             : None
LOCALE           : None.None

pandas           : 0.25.1
numpy            : 1.16.4
pytz             : 2019.2
dateutil         : 2.8.0
pip              : 19.2.2
setuptools       : 41.0.1
Cython           : None
pytest           : 5.0.1
hypothesis       : 4.32.2
sphinx           : 2.1.2
blosc            : None
feather          : None
xlsxwriter       : 1.1.8
lxml.etree       : 4.4.1
html5lib         : None
pymysql          : None
psycopg2         : None
jinja2           : 2.10.1
IPython          : 7.8.0
pandas_datareader: None
bs4              : None
bottleneck       : None
fastparquet      : None
gcsfs            : None
lxml.etree       : 4.4.1
matplotlib       : 3.1.1
numexpr          : 2.7.0
odfpy            : None
openpyxl         : 2.6.2
pandas_gbq       : None
pyarrow          : None
pytables         : None
s3fs             : None
scipy            : 1.3.1
sqlalchemy       : None
tables           : 3.5.2
xarray           : None
xlrd             : 1.2.0
xlwt             : 1.3.0
xlsxwriter       : 1.1.8
</details>
