Fix repeated mangled names in read_csv with duplicate column names

[karthikeyann]

Fixes mangled name bug read_csv with duplicate columns.
mismatch with pandas behavior.

csv file:

A,A,A.1,A,A.2,A,A.4,A,A
1,2,3,4.0,a,a,a.4,a,a
2,4,6,8.0,b,b,b.4,b,a
3,6,2,6.0,c,c,c.4,c,c

A	A	A.1	A	A.2	A	A.4	A	A
A	A.1	A.1.1	A.2	A.2.1	A.3	A.4	A.4.1	A.5

Pandas:

In [1]: import pandas as pd
In [2]: pd.read_csv("test.csv")
Out[2]: 
   A  A.1  A.1.1  A.2 A.2.1 A.3  A.4 A.4.1 A.5
0  1    2      3  4.0     a   a  a.4     a   a
1  2    4      6  8.0     b   b  b.4     b   a
2  3    6      2  6.0     c   c  c.4     c   c

cudf: (21.08 nightly docker)

In [1]: import cudf
In [2]: cudf.__version__
Out[2]: '21.08.00a+238.gfba09e66d8'
In [3]: cudf.read_csv("test.csv")
Out[3]: 
   A  A.1 A.2 A.3 A.4 A.5
0  1    3   a   a   a   a
1  2    6   b   b   b   a
2  3    2   c   c   c   c

This PR fixes this issue.

In [2]: cudf.read_csv("test.csv")
Out[2]: 
   A  A.1  A.1.1  A.2 A.2.1 A.3  A.4 A.4.1 A.5
0  1    2      3  4.0     a   a  a.4     a   a
1  2    4      6  8.0     b   b  b.4     b   a
2  3    6      2  6.0     c   c  c.4     c   c

Related info (sparks):
Spark duplicate column naming.
https://issues.apache.org/jira/browse/SPARK-16896
apache/spark#14745
cudf sparks addon doesn't use libcudf names. So, this PR does not affect it.

[codecov]

Codecov Report

Merging #8645 (b9a4c9e) into branch-21.08 (fba09e6) will increase coverage by 0.01%.
The diff coverage is n/a.

❗ Current head b9a4c9e differs from pull request most recent head 81494a9. Consider uploading reports for the commit 81494a9 to get more accurate results

@@               Coverage Diff                @@
##           branch-21.08    #8645      +/-   ##
================================================
+ Coverage         10.60%   10.61%   +0.01%     
================================================
  Files               109      109              
  Lines             18280    18645     +365     
================================================
+ Hits               1938     1980      +42     
- Misses            16342    16665     +323     

Impacted Files	Coverage Δ
python/cudf/cudf/io/hdf.py	0.00% <0.00%> (ø)
python/cudf/cudf/io/orc.py	0.00% <0.00%> (ø)
python/cudf/cudf/_version.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/abc.py	0.00% <0.00%> (ø)
python/cudf/cudf/api/types.py	0.00% <0.00%> (ø)
python/cudf/cudf/io/dlpack.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/frame.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/index.py	0.00% <0.00%> (ø)
python/cudf/cudf/io/feather.py	0.00% <0.00%> (ø)
python/cudf/cudf/io/parquet.py	0.00% <0.00%> (ø)
... and 44 more

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[vuule]

Just remembered - please add a test case that exercises the behavior change.

[vuule]

rerun tests

[karthikeyann]

@gpucibot merge