More salt-ssh improvements than belong in this issue

- Explict bourne shell, there is no other way to get broad compability
- test python version in SHIM
- inspect SHIM output for errors, and report sensible error results
- Refactor some stuff to consolidate deploy behavior.  We still test and
  attempt deploy in at least 3 other palces yet.
- factor run_wfunc out of single.run for obvious reasons