find_legacy_keymap: try matching with layout order reversed

find_legacy_keymap: try matching with layout order reversed

The lines in kbd-model-map date back to ye olde times (RH's old
system-config-keyboard), and I think predate this bug:

https://bugzilla.redhat.com/show_bug.cgi?id=1039185

where we got strong feedback that, for 'switched' layout setups
like Russian, US English should be the *first* layout and the
native layout the *second* one. This is how anaconda and, as of
recently, gnome-initial-setup configure such cases - but that
means, if we try to use localed to convert these configurations
using kbd-model-map, we get the wrong result (we get "us" as the
console layout). See also:

https://bugzilla.redhat.com/show_bug.cgi?id=1912609

where we first noticed this wasn't working right, but sadly, we
'fixed' it with a not-really-correct bodge in anaconda instead
of doing it properly.

Signed-off-by: Adam Williamson <awilliam@redhat.com>