route: improve -A inet6

route: improve -A inet6

Upstream route command shows non-up routes, it shows reject and nonexthop flags.
And we had "ref" and "use" values mixed up...

function                                             old     new   delta
flagvals                                              32      44     +12
flagchars                                              9      12      +3
INET_setroute                                        767     768      +1
INET6_setroute                                       495     496      +1
set_flags                                             43      39      -4
flags_ipvx                                            16       8      -8
route_main                                           632     623      -9
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 4/3 up/down: 17/-21)             Total: -4 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>