debconf throws errors due to frontend settings

[awijntje]

Heat Template

patch_upload_ve_image.yaml

The following errors are visible in the logs when using this yaml file:
[ 406.825636] cloud-init[1264]: debconf: (TERM is not set, so the dialog frontend is not usable.)
[ 406.834789] cloud-init[1264]: debconf: falling back to frontend: Readline
[ 410.336711] cloud-init[1264]: Unpacking libc6:amd64 (2.23-0ubuntu10) over (2.23-0ubuntu9) ...
[ 416.163342] cloud-init[1264]: Setting up libc6:amd64 (2.23-0ubuntu10) ...
[ 418.922768] cloud-init[1264]: debconf: unable to initialize frontend: Dialog
[ 418.928561] cloud-init[1264]: debconf: (TERM is not set, so the dialog frontend is not usable.)

This can be easily fixed by adding the following statement before the apt-get-section (line 171).
export DEBIAN_FRONTEND=noninteractive