[master] f319a34 Plug minor leak when discarding a vcl

[Federico G. Schwindt]

commit f319a3486f9f2a403bbaf75a2b1044470d8f965f
Author: Federico G. Schwindt <fgsch at lodoss.net>
Date:   Mon Jan 22 02:21:14 2018 +0000

    Plug minor leak when discarding a vcl

diff --git a/bin/varnishd/cache/cache_vcl.c b/bin/varnishd/cache/cache_vcl.c
index d605dcf..aa11668 100644
--- a/bin/varnishd/cache/cache_vcl.c
+++ b/bin/varnishd/cache/cache_vcl.c
@@ -475,6 +475,7 @@ vcl_KillBackends(struct vcl *vcl)
 			break;
 		VTAILQ_REMOVE(&vcl->director_list, d, vcl_list);
 		AN(d->destroy);
+		REPLACE(d->display_name, NULL);
 		d->destroy(d);
 	}
 }