ensure that we downloaded crowbar_register

wget can "succeed" without actually downloading crowbar_register, e.g.

==> controller2: --2014-05-12 22:34:44--  (try: 4)  http://192.168.124.10:8091/suse-11.3/crowbar_register
==> controller2: Connecting to 192.168.124.10:8091...
==> controller2: failed: Connection timed out.
==> controller2: Retrying.
==> controller2: --2014-05-12 22:37:58--  (try: 5)  http://192.168.124.10:8091/suse-11.3/crowbar_register
==> controller2: Connecting to 192.168.124.10:8091...
==> controller2: failed: Connection refused.
==> controller2: chmod:
==> controller2: cannot access `crowbar_register'
==> controller2: : No such file or directory
==> controller2: /tmp/vagrant-shell: line 5: ./crowbar_register: No such file or directory
add set -e to vagrant provision scripts

We don't want any silent failures.