t/lib/HydraTestContext: set queue runner port to 0

This makes the exposer choose a random, available port.

t/Hydra/Config/include.t

@@ -20,6 +20,7 @@ write_file($ctx{'tmpdir'} . "/bar.conf", q|
 |);
 
 is(getHydraConfig(), {
+    queue_runner_metrics_port => 0,
     foo => { bar => "baz" }
 }, "Nested includes work.");
 

t/lib/HydraTestContext.pm

@@ -51,6 +51,7 @@ sub new {
     $ENV{'HYDRA_CONFIG'} = "$dir/hydra.conf";
 
     my $hydra_config = $opts{'hydra_config'} || "";
+    $hydra_config = "queue_runner_metrics_port = 0\n" . $hydra_config;
     if ($opts{'use_external_destination_store'} // 1) {
         $hydra_config = "store_uri = file:$dir/nix/dest-store\n" . $hydra_config;
     }