refresh: Add catching of RequestException in refresh.php

Summary:
PHP Fatal error: Uncaught GuzzleHttp\Exception\ClientException: Client error:
GET https://performance.wikimedia.org/xenon/logs/daily/.RunJobs.log
resulted in a 404 Not Found response: <title>404 Not Found</title>

PHP Fatal error: Uncaught GuzzleHttp\Exception\ClientException: Client error:
GET https://doc.wikimedia.org/cover-extensions/WikibaseQualityConstraints/clover.xml
resulted in a 404 Not Found response: …

Reviewers: Krinkle

Reviewed By: Krinkle

Differential Revision: https://phabricator.wikimedia.org/D1162