Fix some existing wallpaper backup tests

Some of the tests weren't testing what they were designed to test,
likely due to code changes over time. The `testUpdateWallpaperComponent`
tests not explicitly named `delayed` were actually testing the
delayed restore flow.

Bug: 376172272
Flag: EXEMPT test fixes
Test: verified that fixed tests cover the right code
Change-Id: I13566c1bbbba857ecd1f1218a278aea4463d3790