Regression test for Bug #20304
Fixed #20304: file:// URI gets crippled

Net_URL2 internally does not differ between an unset and an empty
authority.

This is an issue for URIs that have an implicit federated non-empty
default authority by their scheme as this is the case for "file" URI
scheme.

To get Net_URL2 still working while not changing all inner guts, a small
fix has been made to Net_URL2::getURL handling the special case for
file:// URI authorities.

This issue has been introduced in 7e28674:

    Fixed #20159: Authority not terminated by slash

ca. 7 months ago.
Prepared 2.0.6