Updating of MAC vendor database

[lukasjuhrich]

We might want to automatically update the mac vendor lookup database.
The vendor data is cached in a local file (usually ~/.cache/mac-vendors.txt), as can be seen in the source code of the package.

To update, it is enough to invoke MacLookup().update_vendors().

Problem: We need to invoke the update on every worker due to the fs-based caching.