init: move property_service.cpp to libinit

service.cpp, which is part of libinit, references symbols in
property_service.cpp, which causes the linker to complain when linking
libinit.a in some situations.

Therefore, we move property_service.cpp to libinit.

Separately, this will make it easier to write tests for
property_service.cpp, which we will want to do in the future.

Test: build, init unit tests
Change-Id: If1cffa8510b97e9436efed3c8ea0724272383eba