tests: avoid using dconf
tests: avoid using dconf

tests/eds/perf reliably fails for me with this warning:

dconf-WARNING **: failed to commit changes to dconf: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name ca.desrt.dconf was not provided by any .service files

and in any case we shouldn't be changing the user's real configuration.

https://bugzilla.gnome.org/show_bug.cgi?id=726973

pwithnall/folks,pwithnall/folks,GNOME/folks,GNOME/folks,GNOME/folks,pwithnall/folks