Workaround missing zip snapshot

At the moment, xenserver installation depends on github snapshots.
Unfortunately, git.openstack.org does not have that capability. This
fix includes:

 - Exit with error code, if a download fails
 - create proper urls, even if they are using the git protocol
 - set git base to github - so we are able to do snapshots

Fixes bug: 1259905

Change-Id: I8d0cf8bf8abb16ee0a4b138a6719409c75e7a146
diff --git a/tools/xen/mocks b/tools/xen/mocks
index ec8679e..3b9b05c 100644
--- a/tools/xen/mocks
+++ b/tools/xen/mocks
@@ -35,7 +35,7 @@
 
 function wget {
     if [[ $@ =~ "failurl" ]]; then
-        exit 1
+        return 1
     fi
     echo "wget $@" >> $LIST_OF_ACTIONS
 }
@@ -77,6 +77,10 @@
     exit 1
 }
 
+function die_with_error {
+    echo "$1" >> $DEAD_MESSAGES
+}
+
 function xe {
     cat $XE_RESPONSE
     {