Upgraded to EOS 4.6.7-20200110135430git7d9a797 in order to get Michael's modification that sends full replies to 'xrdfs hostname query prepare' requests

This storage class is ignored during CREATE, so that we don't need to
set up an archive route just for testing.

This reverts commit 6fbe0298.

Namespace lookup is expensive, so only do it when explicitly requested.

This implementation (unfortunately) introduces one more CLI, but
it makes the 0-byte files migration fully independent from the rest.
The main reason is that the query to extract them from the CASTOR
Nameserver is pretty expensive.
The README.md file and the packaging have been updated accordingly.

This decouples the "cta-admin tf ls" command from looking up path names
in the catalogue, paving the way to remove the path from the DB.