Sync persist property immediately,in case of suddenly remove the battery.

Change-Id: I83c5812c69db532f4675f5dbfa508e55999c8dfe

init/property_service.c

@@ -269,6 +269,7 @@ static void write_persistent_property(const char *name, const char *value)
         return;
     }
     write(fd, value, strlen(value));
+    fsync(fd);
     close(fd);
 
     snprintf(path, sizeof(path), "%s/%s", PERSISTENT_PROPERTY_DIR, name);