Remove hardwired ansolabs urls

Fixes bug 1078618.

The files are no longer available on ansolabs' servers. The files were
put on github, and this change modifies the location used in devstack.

Change-Id: I1f512ad3b52d6b04d0e28ce6a532e11bfede1462
diff --git a/tools/xen/prepare_guest_template.sh b/tools/xen/prepare_guest_template.sh
index baf9c3a..19bd2f8 100755
--- a/tools/xen/prepare_guest_template.sh
+++ b/tools/xen/prepare_guest_template.sh
@@ -60,7 +60,7 @@
     rm -rf $TMP_DIR
 else
     echo "WARNING: no XenServer tools found, falling back to 5.6 tools"
-    TOOLS_URL="http://images.ansolabs.com/xen/xe-guest-utilities_5.6.100-651_amd64.deb"
+    TOOLS_URL="https://github.com/downloads/citrix-openstack/warehouse/xe-guest-utilities_5.6.100-651_amd64.deb"
     wget $TOOLS_URL -O $XS_TOOLS_FILE_NAME
     cp $XS_TOOLS_FILE_NAME "${STAGING_DIR}${XS_TOOLS_PATH}"
     rm -rf $XS_TOOLS_FILE_NAME