Move the image cleanup script with other scripts.

That way, it doesn't get picked by the build into
the out/ directory.

Change-Id: I36548b02b03999ada9efb824fba24f2221b68d78
diff --git a/src/images/cleanup.sh b/scripts/cleanup.sh
similarity index 100%
rename from src/images/cleanup.sh
rename to scripts/cleanup.sh