concat with same column names
#### Code Sample, a copy-pastable example if possible

```python
>>> df1 = pd.DataFrame()
>>> df2 = pd.DataFrame()
>>> df3 = pd.DataFrame()
>>> df1['1'] = range(0,10)
>>> df2['2'] = range(0,20,2)
>>> df3['2'] = range(0,30,3)
>>> df = pd.concat([df1, df2, df3], axis=1)
>>> df
   1   2   2
0  0   0   0
1  1   2   3
2  2   4   6
3  3   6   9
4  4   8  12
5  5  10  15
6  6  12  18
7  7  14  21
8  8  16  24
9  9  18  27
>>> df['2']
    2   2
0   0   0
1   2   3
2   4   6
3   6   9
4   8  12
5  10  15
6  12  18
7  14  21
8  16  24
9  18  27
>>> df['2'] = range(0,50,5)
>>> df
   1   2   2
0  0   0   0
1  1   5   5
2  2  10  10
3  3  15  15
4  4  20  20
5  5  25  25
6  6  30  30
7  7  35  35
8  8  40  40
9  9  45  45
>>>


```
#### Problem description
**why** 
Concat on dataframes containing same column name leads to multiple entries with same column name.(it should append the columns with column_name_1 and column_name_2, similar to merge). On performing actions on the column(as shown in above example) it leads to action replicated to both the columns.

**Version**
3.6.8 (default, Apr 25 2019, 21:02:35) \n[GCC 4.8.5 20150623 (Red Hat 4.8.5-36)]

For documentation-related issues, you can check the latest versions of the docs on `master` here:

https://pandas-docs.github.io/pandas-docs-travis/

If the issue has not been resolved there, go ahead and file it in the issue tracker.

#### Expected Output

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

<details>

[paste the output of ``pd.show_versions()`` here below this line]
commit           : None
python           : 3.6.8.final.0
python-bits      : 64
OS               : Linux
OS-release       : 3.10.0-957.12.2.el7.x86_64
machine          : x86_64
processor        : x86_64
byteorder        : little
LC_ALL           : None
LANG             : en_US.UTF-8
LOCALE           : en_US.UTF-8

pandas           : 0.25.3
numpy            : 1.18.0
pytz             : 2019.3
dateutil         : 2.8.1
pip              : 18.1
setuptools       : 40.6.2
Cython           : None
pytest           : None
hypothesis       : None
sphinx           : None
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : None
html5lib         : None
pymysql          : None
psycopg2         : None
jinja2           : None
IPython          : None
pandas_datareader: None
bs4              : None
bottleneck       : None
fastparquet      : None
gcsfs            : None
lxml.etree       : None
matplotlib       : None
numexpr          : None
odfpy            : None
openpyxl         : None
pandas_gbq       : None
pyarrow          : None
pytables         : None
s3fs             : None
scipy            : 1.4.1
sqlalchemy       : None
tables           : None
xarray           : None
xlrd             : None
xlwt             : None
xlsxwriter       : None

</details>
