BUILD/MINOR: opentracing: fixed compilation with filter enabled

The inclusion of header files proxy.h and tools.h was added to the
addons/ot/include/include.h file.  Without this HAProxy cannot be
compiled if the OpenTracing filter is to be used.
diff --git a/addons/ot/include/include.h b/addons/ot/include/include.h
index 3c0d110..f185a53 100644
--- a/addons/ot/include/include.h
+++ b/addons/ot/include/include.h
@@ -31,8 +31,10 @@
 #include <haproxy/http_htx.h>
 #include <haproxy/http_rules.h>
 #include <haproxy/log.h>
+#include <haproxy/proxy.h>
 #include <haproxy/sample.h>
 #include <haproxy/tcp_rules.h>
+#include <haproxy/tools.h>
 #include <haproxy/vars.h>
 
 #include "config.h"