init: clean up more headers

We don't need everyone including <sys/system_properties.h>

Test: boot bullhead
Change-Id: I73d507e4f273678eaf15947725741e1e3b966cc6
diff --git a/init/service.cpp b/init/service.cpp
index 8cb8dc1..4adbbf0 100644
--- a/init/service.cpp
+++ b/init/service.cpp
@@ -24,6 +24,7 @@
 #include <sys/prctl.h>
 #include <sys/resource.h>
 #include <sys/stat.h>
+#include <sys/system_properties.h>
 #include <sys/time.h>
 #include <sys/wait.h>
 #include <termios.h>