Hotfix/fixes for latest images

updating to the latest provider images raised several issues, which this PR addresses:
  - [x] curl not included in the minimal images.  for chef install, added a check for curl and default to wget if not installed
  - [x] scp not installed in the minimal images.  Added a check for it, and attempt a yum or apt-get install.  This is a bit ugly, and needs to be added to both automators.
  - [x] rackspace new images empirically more susceptible to connection refused errors.  added the tcp_test_ssh and sleep from the latest knife_rackspace gem