init: Replace property_set() with android::base::SetProperty()

Init is no longer a special case and talks to property service just
like every other client, therefore move it away from property_set()
and to android::base::SetProperty().

In doing so, this change moves the initial property set up from the
kernel command line and property files directly into PropertyInit().
This makes the responsibilities between init and property services
more clear.

Test: boot, unit test cases
Change-Id: I36b8c83e845d887f1b203355c2391ec123c3d05f
diff --git a/init/property_service.h b/init/property_service.h
index 8f7d8d9..506d116 100644
--- a/init/property_service.h
+++ b/init/property_service.h
@@ -29,10 +29,7 @@
 
 bool CanReadProperty(const std::string& source_context, const std::string& name);
 
-extern uint32_t (*property_set)(const std::string& name, const std::string& value);
-
-void property_init();
-void property_load_boot_defaults(bool load_debug_prop);
+void PropertyInit();
 void StartPropertyService(int* epoll_socket);
 
 }  // namespace init