max() function - returns wrong value with categorical Series
#### Code Sample, a copy-pastable example if possible

```python
import pandas as pd

# Create demo data for package delivery
df = pd.DataFrame({'package_id': [1, 1, 1, 2, 2, 3],
                   'status': ['Waiting', 'OnTheWay', 'Delivered', 'Waiting', 'OnTheWay', 'Waiting']})

# Status column: Make ordinal
delivery_status_type = pd.CategoricalDtype(categories=['Waiting', 'OnTheWay', 'Delivered'], ordered=True)
df['status'] = df['status'].astype(delivery_status_type)

# Way 1: Looks correct
max1 = df['status'].max()
print(max1)

# Way 2: Incorrect. Prints bad value 'Waiting' instead of correct value 'Delivered'
max2 = max(df['status'])
print(max2)

>>> Delivered      # (is OK)
>>> Waiting        # (is WRONG)
```
#### Problem description

Generic function `max()` return incorrect result on categorical Series.

#### Expected Output

Way 2 (in code) should return correct value `Delivered`,
not bad value `Waiting`

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

<details>

INSTALLED VERSIONS
------------------
commit           : None
python           : 3.7.3.final.0
python-bits      : 64
OS               : Windows
OS-release       : 10
machine          : AMD64
processor        : Intel64 Family 6 Model 94 Stepping 3, GenuineIntel
byteorder        : little
LC_ALL           : None
LANG             : None
LOCALE           : None.None

pandas           : 0.25.1
numpy            : 1.16.5
pytz             : 2019.3
dateutil         : 2.8.0
pip              : 19.2.3
setuptools       : 41.4.0
Cython           : None
pytest           : 5.0.1
hypothesis       : None
sphinx           : 2.2.0
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : 4.4.1
html5lib         : None
pymysql          : None
psycopg2         : None
jinja2           : 2.10.3
IPython          : 7.8.0
pandas_datareader: None
bs4              : None
bottleneck       : None
fastparquet      : None
gcsfs            : None
lxml.etree       : 4.4.1
matplotlib       : 3.1.0
numexpr          : None
odfpy            : None
openpyxl         : None
pandas_gbq       : None
pyarrow          : None
pytables         : None
s3fs             : None
scipy            : None
sqlalchemy       : None
tables           : None
xarray           : None
xlrd             : 1.2.0
xlwt             : None
xlsxwriter       : None

</details>
