Fix empty entry in demo list

[MauricioFauth]

The fetch_versions.py was including an empty entry in the demo server list.

Replaces the legacy RawConfigParser object with ConfigParser(interpolation=None).

- ['master', 'master-config', 'master-http', 'master-config-nopmadb', 'STABLE', 'QA_4_9', 'QA_5_2', '']
+ ['master', 'master-config', 'master-http', 'master-config-nopmadb', 'STABLE', 'QA_4_9', 'QA_5_2']

Before:

After:

[codecov[bot]]

Codecov Report

Merging #162 (b973250) into master (beda0f2) will not change coverage. The diff coverage is 0.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #162 +/- ## ======================================= Coverage 65.78% 65.78% ======================================= Files 75 75 Lines 1505 1505 ======================================= Hits 990 990 Misses 515 515 ```