fix changing of admin password (bnc#788161)

install-chef-suse.sh creates the crowbar proposal from /etc/crowbar/crowbar.json
not from bc-template-crowbar.json, so the crowbar password should be changed in
the former not the latter.

See https://github.com/SUSE-Cloud/crowbar/blob/b68434022652d6a432e2f74e617dcfc8b63cc547/extra/install-chef-suse.sh#L261