Provisioner doesnt check for existence of rsync

While not a big issue (since the error reported relates to rsync not being found), it would be nice if the program reported that Node: w.x.y.z does not have rsync installed.

Start at the Provisioner code path that handles rsync on the target node, then trace how missing-command errors are currently reported. Update the reported failure so it identifies the node and says that rsync is not installed, and verify the resulting provisioning error.

Written by the indexing model from the issue text.