Use UPC mirror for ubuntu iso
diff --git a/ubuntu-14.04/template.json b/ubuntu-14.04/template.json
index f8fdac3..d33a262 100644
--- a/ubuntu-14.04/template.json
+++ b/ubuntu-14.04/template.json
@@ -135,7 +135,7 @@
       "http_directory": "http",
       "iso_checksum": "83aabd8dcf1e8f469f3c72fff2375195",
       "iso_checksum_type": "md5",
-      "iso_url": "http://releases.ubuntu.com/14.04/ubuntu-14.04.2-server-amd64.iso",
+      "iso_url": "http://releases.ubuntu.mirror.dkm.cz/releases/14.04/ubuntu-14.04.2-server-amd64.iso",
       "ssh_username": "{{user `user`}}",
       "ssh_password": "{{user `password`}}",
       "ssh_port": 22,
@@ -183,7 +183,7 @@
       "http_directory": "http",
       "iso_checksum": "83aabd8dcf1e8f469f3c72fff2375195",
       "iso_checksum_type": "md5",
-      "iso_url": "http://releases.ubuntu.com/14.04/ubuntu-14.04.2-server-amd64.iso",
+      "iso_url": "http://releases.ubuntu.mirror.dkm.cz/releases/14.04/ubuntu-14.04.2-server-amd64.iso",
       "ssh_username": "{{user `user`}}",
       "ssh_password": "{{user `password`}}",
       "ssh_port": 22,
@@ -202,7 +202,7 @@
       "format": "qcow2",
       "accelerator": "kvm",
       "disk_size": "{{ user `disk_size`}}",
-      "iso_url": "http://releases.ubuntu.com/14.04/ubuntu-14.04.2-server-amd64.iso",
+      "iso_url": "http://releases.ubuntu.mirror.dkm.cz/releases/14.04/ubuntu-14.04.2-server-amd64.iso",
       "iso_checksum_type": "md5",
       "iso_checksum": "83aabd8dcf1e8f469f3c72fff2375195",
       "http_directory": "http",