test/packet: Default download to /tmp
test/packet: Default download to /tmp

By default, the add_vagrant_box.sh script used to download Vagrant boxes
to the current directory. This can lead to issues when the current
directory is Cilium's [1].

This commit removes the -t flag to download to /tmp and makes that the
default. Now, if -t is given, it will display a warning. This commit
also introduces a new -d <dir> flag to download the Vagrant boxes to a
directory different from /tmp.

1 - https://github.com/cilium/cilium/pull/14045
Signed-off-by: Paul Chaignon <a027184a55211cd23e3f3094f1fdc728df5e0500@cilium.io>

tklauser/cilium,cilium/cilium,tgraf/cilium,michi-covalent/cilium,michi-covalent/cilium,tgraf/cilium,tklauser/cilium,tgraf/cilium,michi-covalent/cilium,tklauser/cilium,tklauser/cilium,michi-covalent/cilium,tklauser/cilium,tgraf/cilium,cilium/cilium,cilium/cilium,michi-covalent/cilium,tgraf/cilium,tgraf/cilium,cilium/cilium,cilium/cilium