Fix install_puppet_on on el8

[gcampbell12]

beaker has support for an el-8-* platform but the install_puppet_on function does not recognise this platform

[codecov]

Codecov Report

Merging #170 (7344f33) into master (ee3b88b) will decrease coverage by 0.02%.
The diff coverage is 100.00%.

❗ Current head 7344f33 differs from pull request most recent head bce5987. Consider uploading reports for the commit bce5987 to get more accurate results

@@            Coverage Diff             @@
##           master     #170      +/-   ##
==========================================
- Coverage   78.09%   78.07%   -0.03%     
==========================================
  Files          15       15              
  Lines        1598     1596       -2     
==========================================
- Hits         1248     1246       -2     
  Misses        350      350              

Impacted Files	Coverage Δ
lib/beaker-puppet/install_utils/foss_utils.rb	70.93% <100.00%> (-0.10%)	⬇️

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[ekohl]

@smortex want to recheck?

[smortex]

👍