util: Don't leak @reply in virSystemdGetMachineNameByPID

@reply is a DBusMessage object returned by virDBusCallMethod in
get machine object call path, dereference it before calling
virDBusCallMethod again to get machine name.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

src/util/virsystemd.c

@@ -247,6 +247,9 @@ virSystemdGetMachineNameByPID(pid_t pid)
     if (virDBusMessageRead(reply, "o", &object) < 0)
         goto cleanup;
 
+    virDBusMessageUnref(reply);
+    reply = NULL;
+
     VIR_DEBUG("Domain with pid %lld has object path '%s'",
               (long long) pid, object);