Update cache_server to point to multiple exec locations

Apparently the location of pip2pi is changnign for different distros
and rather than trying to manage it via a param, which will likley also
have to change, since the command name is the same, there is now
simply an Exec default for a set of paths.

Changed the creates => to unless =>, removed the unused params
from params.pp
Merge branch 'modify_pip2pi_params' of https://github.com/robertstarmer/puppet-COI into modify_pip2pi_params