Trying to fix failing DB builds

Currently, builds like https://travis-ci.org/doctrine/dbal/jobs/440354436 are failing do to an APT issue. Trying to update APT packages as per support recommendation.

tests/travis/install-db2-ibm_db2.sh

@@ -4,6 +4,8 @@ set -ex
 
 echo "Installing extension"
 (
+    # updating APT packages as per support recommendation
+    sudo apt -y -q update
     sudo apt install ksh
 
     cd /tmp