validate_cmd(): Use Puppet::Util::Execution.execute when available
validate_cmd(): Use Puppet::Util::Execution.execute when available

jbondpdx/puppetlabs-stdlib,puppetlabs/puppetlabs-stdlib,yadavnikhil/puppetlabs-stdlib,HelenCampbell/puppetlabs-stdlib,fuel-infra/puppetlabs-stdlib,DavidS/puppetlabs-stdlib