Clean up system service registration. (2nd try)

Bug: 143788029
Test: boot
Test: build/soong/soong_ui.bash --make-mode dist ANDROID_BUILDSPEC=vendor/google/build/app_build_spec.mk
(This build uses java 8, which caused a build failure at the first try)

Test: atest SystemUITests

Change-Id: I352df4e76c9a2e787c9b4216b26d8d5fc84ff369