[Backport 2.19] Always install demo certs if configured with demo certs

[cwperks]

Backport #5517 to 2.19

[codecov]

Codecov Report

❌ Patch coverage is 57.50000% with 17 lines in your changes missing coverage. Please review.
✅ Project coverage is 68.35%. Comparing base (c34e772) to head (2dbbd48).
⚠️ Report is 1 commits behind head on 2.19.

Files with missing lines	Patch %	Lines
...y/tools/democonfig/SecuritySettingsConfigurer.java	55.17%	5 Missing and 8 partials ⚠️
...ecurity/tools/democonfig/CertificateGenerator.java	63.63%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             2.19    #5539      +/-   ##
==========================================
- Coverage   68.37%   68.35%   -0.03%     
==========================================
  Files         348      348              
  Lines       24664    24695      +31     
  Branches     4096     4106      +10     
==========================================
+ Hits        16865    16880      +15     
- Misses       5879     5886       +7     
- Partials     1920     1929       +9     

Files with missing lines	Coverage Δ
...pensearch/security/tools/democonfig/Installer.java	71.34% <ø> (ø)
...ecurity/tools/democonfig/CertificateGenerator.java	76.47% <63.63%> (-16.87%)	⬇️
...y/tools/democonfig/SecuritySettingsConfigurer.java	72.04% <55.17%> (-3.12%)	⬇️

... and 9 files with indirect coverage changes

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