provisioner/shell: remove check for empty env vars config
provisioner/shell: remove check for empty env vars config

TranscendComputing/packer,patricklucas/packer,suma/packer,suma/packer,zyegfryed/packer,TranscendComputing/packer,smerrill/packer,suma/packer,zyegfryed/packer,msabramo/packer,Kaixiang/packer,msabramo/packer,Kaixiang/packer,zyegfryed/packer,msabramo/packer,smerrill/packer,suma/packer,zyegfryed/packer,patricklucas/packer,Kaixiang/packer,TranscendComputing/packer,smerrill/packer,Kaixiang/packer,patricklucas/packer,msabramo/packer,TranscendComputing/packer,smerrill/packer,patricklucas/packer