OpenSSL 1.0.0 added an implementation of TLS session tickets, a
"feature" that let session resumption occur without server-side state
by giving clients an encrypted "ticket" that the client could present
later to get the session going again with the same keys as before.
OpenSSL was giving the keys to decrypt these tickets the lifetime of
the SSL contexts, which would have been terrible for PFS if we had
long-lived SSL contexts. Fortunately, we don't. Still, it's pretty
bad. We should also drop these, since our use of the extension stands
out with our non-use of session cacheing.
Found by nextgens. Bugfix on all versions of Tor when built with
openssl 1.0.0 or later. Fixes bug 7139.
