testing: Determine Debian version in TNC scenarios automatically again

Was statically set to 10 since f3d96b7bc9 ("Version bump to 5.9.1dr1").

testing/tests/tnc/tnccs-20-pdp-eap/pretest.dat

@@ -13,7 +13,7 @@ dave::cat /etc/tnc_config
 carol::echo 0 > /proc/sys/net/ipv4/ip_forward
 dave::echo aabbccddeeff11223344556677889900 > /var/lib/dbus/machine-id
 alice::sed -i "s/NOW/`date +%s`/g" /etc/pts/data1.sql
-alice::sed -i "s/DEBIAN_VERSION/10/" /etc/pts/data1.sql
+alice::sed -i "s:DEBIAN_VERSION:\`. /etc/os-release\; echo \$VERSION_ID\`:" /etc/pts/data1.sql
 alice::cd /usr/local/share/strongswan/templates/database/imv; cat tables.sql data.sql /etc/pts/data1.sql | sqlite3 /etc/db.d/config.db
 alice::chgrp -R www-data /etc/db.d/config.db; chmod -R g+w /etc/db.d/config.db
 alice::/usr/local/bin/init_tnc