xenial64.erb in boxes-3.4.0

- old
+ new

@@ -24,11 +24,11 @@
             <%- else -%>
             "guest_os_type": "Ubuntu_64",
             <%- end -%>
             "headless": true,
 
-            "iso_url": "http://releases.ubuntu.com/16.04/ubuntu-16.04.4-server-amd64.iso",
-            "iso_checksum": "0a03608988cfd2e50567990dc8be96fb3c501e198e2e6efcb846d89efc7b89f2",
+            "iso_url": "http://releases.ubuntu.com/xenial/ubuntu-16.04.5-server-amd64.iso",
+            "iso_checksum": "c94de1cc2e10160f325eb54638a5b5aa38f181d60ee33dae9578d96d932ee5f8",
             "iso_checksum_type": "sha256",
 
             "ssh_username": "vagrant",
             "ssh_password": "vagrant",
             "ssh_timeout": "15m",