qemuxml2argvtest: Don't use privileged mode upfront

When building packages in a clean chroot the QEMU_USER and QEMU_GROUP
don't exist making VirQemuDriverConfigNew fail with privileged=true.

Avoid that by not requiring privileged mode upfront but setting it later
so we skip the user/group existence check.

This solution was suggested by Daniel P. Berrange and tested by Martin
Kletzander.

tests/qemuxml2argvtest.c

@@ -499,9 +499,11 @@ mymain(void)
         return EXIT_FAILURE;
     }
 
-    driver.config = virQEMUDriverConfigNew(true);
+    driver.config = virQEMUDriverConfigNew(false);
     if (driver.config == NULL)
         return EXIT_FAILURE;
+    else
+        driver.config->privileged = true;
 
     VIR_FREE(driver.config->spiceListen);
     VIR_FREE(driver.config->vncListen);