Fix Travis CI build

Author: ojab

script/install-openldap

@@ -6,6 +6,7 @@ BASE_PATH="$( cd `dirname $0`/../test/fixtures/openldap && pwd )"
 SEED_PATH="$( cd `dirname $0`/../test/fixtures          && pwd )"
 
 dpkg -s slapd time ldap-utils gnutls-bin ssl-cert > /dev/null ||\
+  DEBIAN_FRONTEND=noninteractive sudo -E apt-get update  -y --force-yes && \
   DEBIAN_FRONTEND=noninteractive sudo -E apt-get install -y --force-yes slapd time ldap-utils gnutls-bin ssl-cert
 
 sudo /etc/init.d/slapd stop