more vcc coverage

bin/varnishtest/tests/v00016.vtc

@@ -117,6 +117,13 @@ varnish v1 -syntax 4.0 -errvcl {Undefined acl foo} {
 	}
 }
 
+varnish v1 -errvcl {Undefined sub foo} {
+	backend dummy None;
+	sub vcl_recv {
+		call foo;
+	}
+}
+
 # NB: The line break in -errvcl is here on purpose, it prevents
 # a spurious "Only available when" addition to be missed when the
 # foo constructor could be confused with the foo instance name.