MINOR: resolvers: Remove server from named_servers tree when removing a SRV item

When a server is cleaned up because the corresponding SRV item is removed,
we always remove the server from the srvrq's name_servers tree. For now, it
is useless because, if a server was attached to a SRV item, it means it was
already removed from the tree. But it will be mandatory to fix a bug.

(cherry picked from commit 73001ab6e39fb25ff406bbcd3809d0a1fa0131b5)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/src/resolvers.c b/src/resolvers.c
index 20f4cd3..402f03f 100644
--- a/src/resolvers.c
+++ b/src/resolvers.c
@@ -588,6 +588,10 @@
 	memset(&srv->addr, 0, sizeof(srv->addr));
 	srv->svc_port = 0;
 	srv->flags |= SRV_F_NO_RESOLUTION;
+
+	ebpt_delete(&srv->host_dn);
+	ha_free(&srv->host_dn.key);
+
 	HA_SPIN_UNLOCK(SERVER_LOCK, &srv->lock);
 	LIST_DELETE(&srv->srv_rec_item);
 	LIST_APPEND(&srv->srvrq->attached_servers, &srv->srv_rec_item);
@@ -685,7 +689,7 @@
 						if (srv->svc_port == item->port) {
 							/* server found, we remove it from tree */
 							ebpt_delete(node);
-							free(srv->host_dn.key);
+							ha_free(&srv->host_dn.key);
 							goto srv_found;
 						}