smb: fix wsdiscovery unknown device fallback string

Summary:
wasn't using xi18n so <resource> wasn't parsed as markup but rather used
verbatim. also was missing the argument for %1 so the host address wasn't
included

Test Plan: computer.clear() just prior now results in expected "Unknown device @ "::1"" names for the entries

Reviewers: ngraham

Reviewed By: ngraham

Subscribers: kde-frameworks-devel, kfm-devel

Tags: Dolphin, Frameworks

Differential Revision: https://phabricator.kde.org/D27900