Updater (ssh upload): force-overwrite the db.xml.gz

Jerome Mutterer reported that on his setup, mv asks for permission
to overwrite db.xml.gz, so it must somehow default to adding '-i'
to the command-line options. Let's override that setting because we
*know* that we want to overwrite db.xml.gz; that's the whole point
of locking...

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Merge branch 'for-jerome'
Merge branch 'master' of git://github.com/imagej/imagej