watch files now use pre-released tars

[Jonathan Riddell]

Thanks to Harald's nifty neon-sftp-bridge we now have the ability to
find tars before they get released.  So when running watcher jobs on
build.neon.kde.org the debian/watch file is mangled to open the bridge
instead and it can see tars on download.kde.org even when they are
still hidden to the web server as happens a few days before Plasma .0
releases or with Applications releases.  Mind when building these
pre-release tars not to snapshot them into User but keep them in
Release for testing until they get released (consider disabling the
snapshot job so it's clear to everyone).

Jonathan