Description of problem:
Running packstack on a few minimal installations, I noticed it will run into an endless loop if scp is missing on the nodes.

Version-Release number of selected component (if applicable):
openstack-packstack-2012.2.2-0.5.dev318.el6.noarch


How reproducible:
Always

Steps to Reproduce:
1. Setup a host and a node, the latter without installing the scp binary (i.e. openssh-clients package)
2. Run packstage
3. Watch it loop at "Testing if puppet apply is finished : <node IP>_prescript.pp"
  
Actual results:
Endless loop.

Expected results:
Either exit with an error or install what's missing (beforehand, since you know you're going to need it for sure) and continue.

Additional info:
Testing if puppet apply is finished : 10.112.1.30_prescript.pp
DEBUG:root:# ============ ssh : None ==========
DEBUG:root:scp -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null root.1.28:/var/tmp/3ff889d0-da2b-4651-9f52-242afaade21f/manifests/10.112.1.28_prescript.pp.finished /var/tmp/3ff889d0-da2b-4651-9f52-242afaade21f/manifests/10.112.1.28_prescript.pp.log
DEBUG:root:============ STDOUT ==========
DEBUG:root:
DEBUG:root:============= STDERR ==========
DEBUG:root:+ trap t ERR
+ scp -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null root.1.28:/var/tmp/3ff889d0-da2b-4651-9f52-242afaade21f/manifests/10.112.1.28_prescript.pp.finished /var/tmp/3ff889d0-da2b-4651-9f52-242afaade21f/manifests/10.112.1.28_prescript.pp.log
Warning: Permanently added '10.112.1.28' (RSA) to the list of known hosts.
bash: scp: command not found
++ t
++ exit 1