CLOUDSTACK-7143: try to fix jenkins problems with last 2 commits

* bundle install needs to run before running the vbox cleaning scripts,
  so move prepare step before clean step
* feature branches have / in their name which is a bad character to
  put into filenames

tools/appliance/build.sh

@@ -499,13 +499,13 @@ function hyperv_export() {
 ###
 
 function main() {
+  prepare
   if [ "${clean_vbox}" == "1" ]; then
     clean_vbox --delete
     add_on_exit clean_vbox --delete
   else
     stop_vbox # some extra encouragement for virtualbox to stop things
   fi
-  prepare
   create_definition
   veewee_destroy # in case of left-over cruft from failed build
   add_on_exit veewee_destroy