images_to_archives.tcl: don't modify registry until all archives have been successfully created, and don't delete old image dirs until registry has been successfully changed. This should allow users to at least go back to 1.9 if conversion fails.
images_to_archives.tcl: don't modify registry until all archives have been successfully created, and don't delete old image dirs until registry has been successfully changed. This should allow users to at least go back to 1.9 if conversion fails.

git-svn-id: 620571fa9b4bd0cbce9a0cf901e91ef896adbf27@79445 d073be05-634f-4543-b044-5fe20cf6d1d6

danchr/macports-base,neverpanic/macports-base,danchr/macports-base,macports/macports-base,macports/macports-base,neverpanic/macports-base