Fixed logging in ngx_http_wait_request_handler().

If c->recv() returns 0 there is no sense in using ngx_socket_errno for
logging, its value meaningless.  (The code in question was copied from
ngx_http_keepalive_handler(), but ngx_socket_errno makes sense there as it's
used as a part of ECONNRESET handling, and the c->recv() call is preceeded
by the ngx_set_socket_errno(0) call.)

src/http/ngx_http_request.c

diff --git a/src/http/ngx_http_request.c b/src/http/ngx_http_request.c
index a19d327..87df262 100644
--- a/src/http/ngx_http_request.c
+++ b/src/http/ngx_http_request.c
@@ -456,7 +456,7 @@
     }
 
     if (n == 0) {
-        ngx_log_error(NGX_LOG_INFO, c->log, ngx_socket_errno,
+        ngx_log_error(NGX_LOG_INFO, c->log, 0,
                       "client closed connection");
         ngx_http_close_connection(c);
         return;