IMMS tests: fix broken tests

The test relied on another unrelated test
initializing the ContentProvider that DeviceConfig uses.

After Ia6f2ee781c431088cbb3417c1b6bac86cfce4c13, this is
no longer happening. Working around it for now to unblock tests.

Fixes: 272229177
Test: atest DefaultImeVisibilityApplierTest
Change-Id: I51e4f28b885b6dbdf64e759d5978b89c9039db6b