Make "config" and "iso" test attributes accessible

tests/default.nix

@@ -25,6 +25,7 @@ let
 
     renderDhallInit = path: args:
       hostPkgs.runCommand "init.xml" {
+        preferLocalBuild = true;
         buildInputs = [ hostPkgs.dhall ];
         initConfig = path;
         initArgs = args;

tests/driver-config.xml

@@ -9,6 +9,7 @@
     <service name="RM"/>
     <service name="CPU"/>
     <service name="LOG"/>
+    <service name="TRACE"/>
   </parent-provides>
   <default-route>
     <any-service>

tests/driver-nova.nix

@@ -91,18 +91,19 @@ let
         		return
         	}
 
+        	global spawn_id
+        	spawn ${hostPkgs.qemu_test}/bin/qemu-system-x86_64 -cdrom ${iso} -nographic \
+        		-m size=${toString qemuMem}
+        	wait_for_output $wait_for_re $timeout_value $spawn_id
+        }
+
+	# TODO: not in TCL
         	global env
         	set out $env(out)
 
         	set fd [open "$out/nix-support/hydra-build-products" w]
         	puts $fd "file iso ${iso}"
         	close $fd
-
-        	global spawn_id
-        	spawn ${hostPkgs.qemu_test}/bin/qemu-system-x86_64 -cdrom ${iso} -nographic \
-        		-m size=${toString qemuMem}
-        	wait_for_output $wait_for_re $timeout_value $spawn_id
-        }
       '';
 
       driver = with hostPkgs;
@@ -129,7 +130,7 @@ let
 
       test = passMeta (runTests driver);
 
-    in test // { inherit driver test; };
+    in test // { inherit driver iso test; config = testConfig; };
 
 in {
   callTest = path: args: