Rework how we strip remote DBus errors

Rework how we strip remote DBus errors

 * This is necessary because sometimes we don't want to complain,
   for expected errors, when running nested operations.
 * The fact that we have to do this is silly, and soon there
   will be a solution in glib itself.

https://bugzilla.gnome.org/show_bug.cgi?id=688165