init: Run restorecon_recursive asynchronously

restorecon_recursive may take a long time if there are a lot of files on
the volume.  This can trigger a watchdog timeout in any process that
tries to set a property while it is running.  Fix this by running
restorecon_recursive in its own process.

See https://jira.lineageos.org/browse/BUGBASH-555

Change-Id: I2ce26ff2b5bfc9a133ea42f4dbac50a3ac289c04
diff --git a/init/property_service.h b/init/property_service.h
index 9a5b6f6..9251722 100644
--- a/init/property_service.h
+++ b/init/property_service.h
@@ -26,6 +26,8 @@
     const char* name;
 };
 
+extern bool PropertyChildReap(pid_t pid);
+
 void property_init(void);
 void property_load_boot_defaults(void);
 void load_persist_props(void);