SSL: reset ready flag if recv(MSG_PEEK) found no bytes in socket.

Previously, connection hung after calling ngx_http_ssl_handshake() with
rev->ready set and no bytes in socket to read.  It's possible in at least the
following cases:

 - when processing a connection with expired TCP_DEFER_ACCEPT on Linux
 - after parsing PROXY protocol header if it arrived in a separate TCP packet

Thanks to James Hamlin.

src/http/ngx_http_request.c

diff --git a/src/http/ngx_http_request.c b/src/http/ngx_http_request.c
index a07d5e4..0ee145d 100644
--- a/src/http/ngx_http_request.c
+++ b/src/http/ngx_http_request.c
@@ -652,6 +652,7 @@
 
     if (n == -1) {
         if (err == NGX_EAGAIN) {
+            rev->ready = 0;
 
             if (!rev->timer_set) {
                 ngx_add_timer(rev, c->listening->post_accept_timeout);