Debuntu: add apt-transport-https

I don't see anywhere we bring this in, especially on a minimal build.
In 2020 it seems like a base dependency, put it alongside
software-properties-common that installs the other apt helper bits.

Change-Id: I5b079eac4912cb4a164e9aa6158ed106a28f576c

diskimage_builder/elements/base/pre-install.d/03-baseline-tools

@@ -12,6 +12,6 @@ case $DISTRO_NAME in
         # Note: add-apt-repository would be nice for RPM platforms too - so when we
         # need something like it, create a wrapper in dpkg/bin and fedora/bin.
         apt-get -y update
-        install-packages software-properties-common
+        install-packages software-properties-common apt-transport-https
         ;;
 esac

releasenotes/notes/apt-transport-https-e4856cb9e2f8422c.yaml

@@ -0,0 +1,4 @@
+---
+update:
+  - |
+    Add ``apt-transport-https`` package as a base dependency for Debuntu images.