ffserver: don't leak poll_table if poll fails

Should fix Coverity Scan issue #732265
Signed-off-by: Reynaldo H. Verdejo Pinochet <r.verdejo@sisa.samsung.com>

ffserver.c

@@ -747,8 +747,10 @@ static int http_server(void)
         do {
             ret = poll(poll_table, poll_entry - poll_table, delay);
             if (ret < 0 && ff_neterrno() != AVERROR(EAGAIN) &&
-                ff_neterrno() != AVERROR(EINTR))
+                ff_neterrno() != AVERROR(EINTR)) {
+                av_free(poll_table);
                 return -1;
+            }
         } while (ret < 0);
 
         cur_time = av_gettime() / 1000;