BUG: ssl: send payload gets corrupted if tune.ssl.maxrecord is used

We were using "tune.ssl.maxrecord 2000" and discovered an interesting
problem: SSL data sent from the server to the client showed occasional
corruption of the payload data.

The root cause was:
When ssl_max_record is smaller than the requested send amount
the ring buffer wrapping wasn't properly adjusting the
number of bytes to send.

I solved this by selecting the initial size based on the number
of output bytes that can be sent without splitting _before_ checking
against ssl_max_record.