gd2e0724afc moved our library versions into their own variables named
FULL_SO_VERSION. They're no longer used and interfere with
tools/release-update-debian-soversions.sh so remove them.
Fix some shellcheck warnings in release-update-debian-soversions.sh
while we're here.
Bug: 14778
Change-Id: I0eb0bb4ab4c482bdb8a94f8c18aa04c6c83c781b
Reviewed-on: https://code.wireshark.org/review/28068
Reviewed-by: Gerald Combs <gerald@wireshark.org>
Petri-Dish: Gerald Combs <gerald@wireshark.org>
Tested-by: Petri Dish Buildbot
Reviewed-by: Anders Broman <a.broman58@gmail.com>