Fixed leaking configurable SSL error details.

Fixed leaking configurable SSL error details.

Trunk r11496 "Configurable SSL error details messages" correctly disabled
collection of HTTP statistics for non-HTTP header fields, such as configurable
SSL error details. However, it also incorrectly disabled deletion of those
non-HTTP header fields.

Configurable SSL error details are only created during [re]configuration time,
so the leak went unnoticed since 2011-06-17, but the same bug caused a major
runtime annotation leak later (r12413) until the new annotation code was
redesigned to avoid using HttpHeader (r12779).