Resolve "Logout of Geo secondary takes you to primary login page"

What does this MR do?

When you initially log in to a Geo secondary node, it redirects you to the primary node, you log in there, and it then takes you back to the secondary. When you log out, it also takes you to the primary login screen. However logging in again will log the user into the primary.

The changes introduced in this MR redirect the user back to the secondary node after a log out on the secondary and logging into the primary.

What are the relevant issue numbers?

Closes #4459 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• ~~Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.~~
• EE specific content should be in the top level /ee folder
• For a paid feature, have we considered GitLab.com plans, how it works for groups, and is there a design for promoting it to users who aren't on the correct plan?