Use pba authentication instead of authutils (backport #1505)

[mergify]

This is an automatic backport of pull request #1505 done by Mergify.
Cherry-pick of ef9d161 has failed:

On branch mergify/bp/gvmd-20.08/pr-1505
Your branch is up to date with 'origin/gvmd-20.08'.

You are currently cherry-picking commit ef9d161f3.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   CHANGELOG.md
	modified:   src/CMakeLists.txt
	modified:   src/gvmd.c
	new file:   src/manage_authentication.c
	new file:   src/manage_authentication.h
	modified:   src/manage_sql.c

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   .gitignore

To fix up this pull request, you can check it out locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

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