Fix feature check for haproxy in VTC for the tls hello example/test.

examples/tls/hello/cafe.vtc

@@ -4,7 +4,7 @@ varnishtest "cafe example with TLS offload"
 
 feature ignore_unknown_macro
 
-feature cmd {haproxy --version 2>&1 | grep -q 'HA-Proxy version'}
+feature cmd {which haproxy}
 
 # Use haproxy to forward the non-TLS request from the VTC client below to
 # the Ingress TLS port.