The printers in print dialog should not change position.

The FusedPrintersProvider was not ensuring the existing printers
are at the same position when a new dataset is loaded. As a result
the printers were moving in the UI and sometimes the currently
selected one changed. Now the provider makes sure printers are in
the same position.

bug:10748884

Change-Id: I7c6cd5b1b38fdb615ceaae87806b413272ffba18