Say what holds the address, rather than that it is held

dnsmasq cannot bind 127.0.0.54 and the module's own comment claims that address
is free. Which of those is wrong is the question, and naming the holder answers
it — assuming would be issue 012's mistake, where two things changed and the
plausible one was blamed.

test/integration/mesh.test.ts

@@ -1403,7 +1403,9 @@ test("a service is reached by a name under the machine it runs on", {
       `journal:\n${(await on(machine, `journalctl -u dnsmasq -n 25 --no-pager`)).out}\n` +
       `its config:\n${(await on(machine, `cat /etc/dnsmasq.conf`)).out}\n` +
       `what the mesh wrote:\n${(await on(machine, `cat /etc/mesh-resolver/nodes.conf`)).out}\n` +
-      `resolv.conf:\n${(await on(machine, `cat /etc/resolv.conf`)).out}`);
+      `resolv.conf:\n${(await on(machine, `cat /etc/resolv.conf`)).out}\n` +
+      `what holds a loopback address:\n` +
+      `${(await on(machine, `ss -lntup | grep 127.0.0 || echo none`)).out}`);
   }
 
   // Through the machine's own resolver, by the path an application actually takes: nsswitch, then