Fix cmsImportContest when multiple IPs are provided

[wil93]

The cmsImportContest command fails when some participations specify multiple IPs separated by comma

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This change is 

[codecov]

Codecov Report

Merging #1147 into master will decrease coverage by 0.04%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #1147      +/-   ##
==========================================
- Coverage   61.99%   61.95%   -0.05%     
==========================================
  Files         230      230              
  Lines       16604    16604              
==========================================
- Hits        10294    10287       -7     
- Misses       6310     6317       +7     

Flag	Coverage Δ
#functionaltests	45.66% <0.00%> (+0.07%)	⬆️
#unittests	43.29% <0.00%> (ø)

Impacted Files	Coverage Δ
cmscontrib/ImportContest.py	80.00% <0.00%> (ø)
cms/service/EvaluationService.py	65.95% <0.00%> (-1.60%)	⬇️
cms/service/ProxyService.py	57.44% <0.00%> (-1.60%)	⬇️
cms/server/contest/handlers/taskusertest.py	42.42% <0.00%> (-1.22%)	⬇️
cms/grading/scoring.py	75.58% <0.00%> (-1.17%)	⬇️
cms/server/admin/handlers/dataset.py	24.76% <0.00%> (-0.93%)	⬇️
cms/io/rpc.py	90.78% <0.00%> (-0.35%)	⬇️
cms/io/service.py	69.51% <0.00%> (ø)
cms/server/admin/handlers/base.py	67.79% <0.00%> (ø)
cms/grading/Job.py	89.57% <0.00%> (+0.47%)	⬆️
... and 3 more

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[andreyv]

Thanks, looks good and works fine.

In the italy_yaml loader, the list syntax could be supported as well in the future:

    ip:
      - "192.168.0.0/24"
      - "10.0.0.0/8"