Newly installed workbenches are not on enabled nor disabled list, so
they were treated as disabled. That behaviur could be confusing for
the user as a newly installed workbench was not shouwing up on the
workbench list. This commit changes that behaviour and new workbenches
are enabled by default.
Reported-by: r-frank
Signed-off-by: Przemo Firszt <przemo@firszt.eu>