MINOR: ssl: Remove unused variable "need_out".

MINOR: ssl: Remove unused variable "need_out".

The "need_out" variable was used to let the ssl code know we're done
reading early data, and we should start the handshake.
Now that the handshake function is responsible for taking care of reading
early data, all that logic has been removed from ssl_sock_to_buf(), but
need_out was forgotten, and left. Remove it know.
This patch was submitted by William Dauchy <w.dauchy@criteo.com>, and should
fix github issue #434.
This should be backported to 2.0 and 2.1.

(cherry picked from commit 7f4f7f140f6b03b61d1b38260962db235c42c121)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>