Randomly generated SSH Password not set unless communicator type is explicitly set to ssh

[shubhang93]

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Overview of the Issue

The build variable Password returns an empty string if it's not explicitly set using the ssh_password option. When ssh_password is set it works fine.

Reproduction Steps

Steps to reproduce this issue

Plugin and Packer version

packer: v1.10.0 Plugin: v2.1.3

From packer version

Simplified Packer Buildfile

If the file is longer than a few dozen lines, please include the URL to the gist of the log or use the Github detailed format instead of posting it directly in the issue.

build {
  sources = [
    "..."
  ]

  provisioner "shell" {
        script = "scripts/setup.sh"
	execute_command =  "chmod +x {{ .Path }}; {{ .Vars }}  bash -x -l '{{ .Path }}'"
	environment_vars = [
        "ROOT_PSSWD=${build.Password}",
	"USER_ID=${build.User}",
	"BUILD_ID=${build.ID}",
    ]
  }
}

setup.sh

echo "PASSWORD = ${ROOT_PSSWD}"

output

PASSWORD=<empty_string>

Operating system and Environment details

OS, Architecture, and any other information you can provide about the environment.

Log Fragments and crash.log files

 azure-arm...: temp admin user: 'user'
 azure-arm... temp admin password: '22wlrlNpqTPw6yrDKwwUaxdtL9eta34q'

Set the env var PACKER_LOG=1 for maximum log detail.

Remote command exited with '1': chmod +x /tmp/script_7867.sh; BUILD_ID='ERR_ID_NOT_IMPLEMENTED_BY_BUILDER' C_FORCE_ROOT='True'  
ROOT_PSSWD='' bash -x -l '/tmp/script_7867.sh'