Currently `/etc/debian_version` for Debian/buster systems includes:
buster/sid
So until we get the according version number via base-files, also
check for the codename instead. Make it more generic so it works for
any upcoming release that uses ".*/sid", to not run into the issue
again with e.g. the upcoming Debian/release codenamed bullseye (the
release expected after buster).
Thanks: Manuel Montecelo for improving my initial version
Change-Id: I59e6adea98b6c228daa2b5ebe14872c4a35b8920