Make the dowgrade debconf priority critical so that for sure users will see and read it

debian/mariadb-server-5.5.postrm

@@ -52,9 +52,9 @@ if [ "$1" = "purge" -a ! \( -x /usr/sbin/mysqld -o -L /usr/sbin/mysqld \) ]; the
   rm -f /var/log/mysql.{log,err}{,.0,.[1234567].gz}
   rm -rf /var/log/mysql
 
-  db_input high maria-server-5.5/postrm_remove_databases || true
+  db_input high mysql-server-5.5/postrm_remove_databases || true
   db_go || true
-  db_get maria-server-5.5/postrm_remove_databases || true
+  db_get mysql-server-5.5/postrm_remove_databases || true
   if [ "$RET" = "true" ]; then
     # never remove the debian.cnf when the databases are still existing
     # else we ran into big trouble on the next install!

debian/mariadb-server-5.5.preinst

@@ -81,7 +81,7 @@ for i in `ls $DATADIR/debian-*.flag 2>/dev/null`; do
 done
 if [ "$show_downgrade_warning" = 1 ]; then
   db_fset mariadb-server-5.5/really_downgrade seen false || true
-  db_input medium mariadb-server-5.5/really_downgrade || true
+  db_input critical mariadb-server-5.5/really_downgrade || true
   db_go
   db_get mariadb-server-5.5/really_downgrade || true
   if [ "$RET" = "true" ]; then