SPDY: fixed "too long header line" logging.

This fixes possible one byte buffer overrun and makes sure ellipsis are
always added, see 21043ce2a005.

src/http/ngx_http_spdy.c

diff --git a/src/http/ngx_http_spdy.c b/src/http/ngx_http_spdy.c
index 3c57882..010b803 100644
--- a/src/http/ngx_http_spdy.c
+++ b/src/http/ngx_http_spdy.c
@@ -2656,11 +2656,10 @@
 
         if (rest > NGX_MAX_ERROR_STR - 300) {
             rest = NGX_MAX_ERROR_STR - 300;
-            p[rest++] = '.'; p[rest++] = '.'; p[rest++] = '.';
         }
 
         ngx_log_error(NGX_LOG_INFO, r->connection->log, 0,
-                      "client sent too long header name or value: \"%*s\"",
+                      "client sent too long header name or value: \"%*s...\"",
                       rest, p);
 
         return NGX_DECLINED;