Cache selfservice tabs (don't reload when changing tabs)

See commit 3b6ed288c969e3dbbb4cc3c2b8ec53a43a87a60d for a detailed
explanation.

refs #12696

Change-Id: I068b98c8e2f43ae8ed0b55b0df124109fbee2dbd
Merge "Cache selfservice tabs (don't reload when changing tabs)"