provisioner/shell: add more tests for UnixReader
provisioner/shell: add more tests for UnixReader

TranscendComputing/packer,Kaixiang/packer,TranscendComputing/packer,suma/packer,Kaixiang/packer,Kaixiang/packer,TranscendComputing/packer,suma/packer,TranscendComputing/packer,Kaixiang/packer,suma/packer,suma/packer