Deploy: Upgrade script mapped drives

If the upgrade script has mapped a drive and crashes it should not leave that drive behind. This includes when doing it through pushd.
Also check that mapping drives in this way does not disturb current mapped drives. As one of the server tests make sure that drives are correctly mapped (confirm with Chris):

1. Data drive D
1. Scripting drive U
1. One other?

Finally if running on an instrument that cannot access a network location (e.g. R78) it should give you an error message and an option of mapping using fed credentials (see deply script)