Geo sign out broken

Summary

A user can not sign out of a secondary Geo node. The result is the same weather the user is signed in on the primary or not.

This issue does go away after restarting the secondary node, so it is easy for the user to fix once they discover that they need to restart, but it would be better if it worked the first time.

Steps to reproduce

1. Set up Geo and do not restart the secondary node.
2. Sign in to a secondary Geo node on the Web interface.
3. Click on the avatar and click Sign out.

What is the current bug behavior?

"You cannot do writing operations on a secondary GitLab Geo instance"

What is the expected correct behavior?

Sign the user out.

Relevant logs and/or screenshots

This is a log of the first try where the logout results in an error everything

This is a log where I continue clicking on log-out a few times 🔨 and it worked! everything_again

This was on a fresh installation of Ubuntu 16.04 with GitLab 9.1.2

/cc @brodock