Setup Selenium only if configured

This avoids failures on pull requests.
Signed-off-by: Michal Čihař <michal@cihar.com>

ci/setup-env

@@ -6,6 +6,6 @@ mysql -e 'DROP DATABASE IF EXISTS weblate;'
 mysql -e 'CREATE DATABASE weblate CHARACTER SET utf8 COLLATE utf8_general_ci;'
 psql -c 'DROP DATABASE IF EXISTS weblate;' -U postgres
 psql -c 'CREATE DATABASE weblate;' -U postgres
-if [ -n "$CI_SELENIUM" ] ; then
+if [ -n "$CI_SELENIUM" -a -n "$SAUCE_USERNAME" -a -n "$SAUCE_ACCESS_KEY" ] ; then
     curl -L https://gist.githubusercontent.com/santiycr/5139565/raw/sauce_connect_setup.sh | bash 
 fi