Fix: Don't set management server ID if cookie isn't set.

[jmgsky]

Description

This PR prevents the frontend from setting MS_ID if the "managementserverid" cookie isn't set.

We upgraded to 4.22.1.0 yesterday and non-root-admins couldn't log in with SAML, they were presented with a blank white page and some errors in the javascript console. After a little time in the debugger, I chased it down to this change setting MS_ID in localstorage to "undefined", causing downstream issues in store/modules/user.js.

Fixes: #13277

Types of changes

• Breaking change (fix or feature that would cause existing functionality to change)
• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Enhancement (improves an existing feature and functionality)
• Cleanup (Code refactoring and cleanup, that may add test cases)
• Build/CI
• Test (unit or integration test code)

Feature/Enhancement Scale or Bug Severity

Feature/Enhancement Scale

• Major
• Minor

Bug Severity

• BLOCKER
• Critical
• Major
• Minor
• Trivial

Screenshots (if appropriate):

How Has This Been Tested?

Rebuilt the UI and swapped it in place live on our management server.

How did you try to break this feature and the system with this change?