Use a new FatalServerError exception for SSL certificate failures

Failures in SSL certificate verification are unlikely to be fixed by
just retrying the request. This commit introduces a new FatalServerError
class for this (and maybe other) server error.

Change-Id: I19bf597d967e753b944bd5e7ef6c21b06bc900d7
Merge "Use a new FatalServerError exception for SSL certificate failures"