configs: rpi3: only remove resize script/link if they exist

On some RPi3 images, e.g Ubuntu Server there is no resize init script,
and these commands would fail trying to convert such an image.

This can also be useful on Raspbian images, if they have been booted
once before they are converted using "mender-convert"

Changelog: None

Signed-off-by: Mirza Krak <mirza.krak@northern.tech>

configs/raspberrypi_config

@@ -62,6 +62,8 @@ function platform_modify() {
   run_and_log_cmd "sudo ln -fs /sbin/fw_printenv work/rootfs/sbin/fw_setenv"
 
   # Remove original 'resize2fs_once' script and its symbolic link.
-  run_and_log_cmd "sudo unlink work/rootfs/etc/rc3.d/S01resize2fs_once"
-  run_and_log_cmd "sudo rm work/rootfs/etc/init.d/resize2fs_once"
+  if [ -L work/rootfs/etc/rc3.d/S01resize2fs_once ]; then
+    run_and_log_cmd "sudo unlink work/rootfs/etc/rc3.d/S01resize2fs_once"
+  fi
+  run_and_log_cmd "sudo rm -f work/rootfs/etc/init.d/resize2fs_once"
 }