Have production and Labs Redis sessions use same structure.

The actual wgObjectCaches line has been moved into CommonSettings.php.
The only difference now is the IP(s).

This facilitates re-using this IP for GettingStarted, without
labs-specific GettingStarted configuration.

Bug: 59838
Change-Id: I4aec78765eb7a9c4ebeed35bd7f13a64c31c5f58