Random certificate served on each request when no vhost matched

[Zenexer]

Tracked as CVE-2018-19148, though the status as a vulnerability is disputed. Potential for information disclosure, though in most circumstances the same information would be available in CT logs or through passive DNS. Workaround provided in #1303.

Currently attempting to identify when the issue was introduced.

[mholt]

Change already proposed in #2339.