Use new password script names
Use tripleo-puppet-elements

images.sh was still pointing at tripleo-image-elements so it wasn't
finding the files it needed.
Don't fail if firewalld is not installed

firewalld is not installed on the Fedora cloud images, which means
it can't be stopped or masked during the step that makes the
system use iptables.  Print a message instead of failing the
script in that situation.
Make sure which is installed