Try to remove opcache disable in travis.

.travis.yml

@@ -34,7 +34,6 @@ before_script:
   - composer install
   - uname -a
   - date
-  - phpenv config-add ./tests/travis/php.ini # disables Zend OPCache
   - php -r "var_dump(gd_info());"
   - mysql -e 'create database piwik_test;'
   - ./tests/travis/prepare.sh