test(fab_cli): tag tests that need internet so they can be skipped

[jnahmias]

tag tests that need to download the FAB-Skeleton with 'needs_inet'. This will
allow them to easily be skipped when running in an environment that doesn't
have internet connectivity, such as the Debian build servers.

[codecov]

Codecov Report

Merging #1880 (c0a0277) into master (328adb6) will decrease coverage by 0.10%.
The diff coverage is n/a.

❗ Current head c0a0277 differs from pull request most recent head b521672. Consider uploading reports for the commit b521672 to get more accurate results

@@            Coverage Diff             @@
##           master    #1880      +/-   ##
==========================================
- Coverage   77.74%   77.64%   -0.11%     
==========================================
  Files          70       70              
  Lines        8560     8556       -4     
==========================================
- Hits         6655     6643      -12     
- Misses       1905     1913       +8     

Flag	Coverage Δ
python	77.64% <ø> (-0.11%)	⬇️

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Impacted Files	Coverage Δ
flask_appbuilder/base.py	78.05% <0.00%> (-2.95%)	⬇️
flask_appbuilder/api/__init__.py	96.40% <0.00%> (-0.02%)	⬇️

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