Geo: Validate GitLab does not auto-upgrade PostgreSQL by default

With !4115 (merged) (issue #5251 (closed)), GitLab will not automatically upgrade PostgreSQL by default, if it detects Geo.

Test setup

• Setup Geo with separate databases, with GitLab 12.9.X
• Verify DB nodes are on PG 10.X
• Don't disable automatic PG upgrades
• Validate the setup: Run GitLab QA Geo specs (excluding SSH tests)

GitLab Package Upgrade Test

• Upgrade to GitLab 12.10-pre package built with !4115 (merged)
• Run GitLab QA Geo specs (excluding SSH tests)

Expectation

• PostgreSQL does not get upgraded on any of the 3 DB nodes
• QA Geo specs pass

• Open follow up issues, if any