SSL: raised limit for sessions stored in shared memory.

SSL: raised limit for sessions stored in shared memory.

Upstream SSL sessions may be of a noticeably larger size with tickets
in TLSv1.2 and older versions, or with "stateless" tickets in TLSv1.3,
if a client certificate is saved into the session.  Further, certain
stateless session resumption implemetations may store additional data.

Such one is JDK, known to also include server certificates in session
ticket data, which roughly doubles a decoded session size to slightly
beyond the previous limit.  While it's believed to be an issue on the
JDK side, this change allows to save such sessions.

Another, innocent case is using RSA certificates with 8192 key size.