SSL: fixed ngx_ssl_recv() to reset c->read->ready after errors.

SSL: fixed ngx_ssl_recv() to reset c->read->ready after errors.

With this change, behaviour of ngx_ssl_recv() now matches ngx_unix_recv(),
which used to always reset c->read->ready to 0 when returning errors.

This fixes an infinite loop in unbuffered SSL proxying if writing to the
client is blocked and an SSL error happens (ticket #2418).

With this change, the fix for a similar issue in the stream module
(6868:ee3645078759), which used a different approach of explicitly
testing c->read->error instead, is no longer needed and was reverted.