fillna is broken for Datetime columns [regression]
In 823af7639b94a39609c06a2228ba9e0f31155724 a call to `block._try_coerce_args()` was incorrectly replaced with call to `block._can_hold_element()` (I think under assumption that all block types have identical implementations of `_try_coerce_args` which is not true).

For Datetime blocks this leads to blowing up with `RecursionError: maximum recursion depth exceeded in comparison`.

Prior to the commit I indicated it worked fine, so I consider this a regression.

#### Small reproducer
```python
import pandas as pd
import numpy as np
from io import StringIO as sio

d1 = pd.read_csv(sio('2010,\n,\n2000\n'),header=None,parse_dates=[0])
f1 = np.dtype('datetime64[ms]').type('1970-01-01').astype('datetime64[ms]')
d1[0].fillna(f1)
```
#### Problem description
When the reproducer is launched, it's output is a long stacktrace caused by `RecursionError`.

#### Expected Output
The sample should not raise.

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

<details>

commit           : None
python           : 3.6.8.final.0
python-bits      : 64
OS               : Linux
OS-release       : 4.15.0-47-generic
machine          : x86_64
processor        : x86_64
byteorder        : little
LC_ALL           : None
LANG             : en_US.UTF-8
LOCALE           : en_US.UTF-8

pandas           : 0.25.0rc0+67.g2ed1f28cf
numpy            : 1.16.2
pytz             : 2018.4
dateutil         : 2.6.0
pip              : 10.0.1
setuptools       : 39.0.1.post20180504
Cython           : 0.29.6
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              : 4.7.1
bottleneck       : None
fastparquet      : None
gcsfs            : None
lxml.etree       : None
matplotlib       : None
numexpr          : None
odfpy            : None
openpyxl         : None
pandas_gbq       : None
pyarrow          : 0.9.0
pytables         : None
s3fs             : None
scipy            : 1.2.1
sqlalchemy       : None
tables           : None
xarray           : None
xlrd             : None
xlwt             : None
xlsxwriter       : None

</details>

#### Proposed solution
Revert the changes to `fillna()` function here: https://github.com/pandas-dev/pandas/commit/823af7639b94a39609c06a2228ba9e0f31155724?diff=unified#diff-8f51ce8697bdff680b3f71b196c582eeL388