ip route: Do not imply pref and ttl-propagate are per nexthop

ip route: Do not imply pref and ttl-propagate are per nexthop

Currently `ip -6 route show` gives us this output:

sharpd@eva ~/i/ip (master)> ip -6 route show
::1 dev lo proto kernel metric 256 pref medium
4:5::6:7 nhid 18 proto static metric 20
        nexthop via fe80::99 dev enp39s0 weight 1
        nexthop via fe80::44 dev enp39s0 weight 1 pref medium

Displaying `pref medium` as the last bit of output implies
that the RTA_PREF is a per nexthop value, when it is infact
a per route piece of data.

Change the output to display RTA_PREF and RTA_TTL_PROPAGATE
before the RTA_MULTIPATH data is shown:

sharpd@eva ~/i/ip (master)> ./ip -6 route show
::1 dev lo proto kernel metric 256 pref medium
4:5::6:7 nhid 18 proto static metric 20 pref medium
        nexthop via fe80::99 dev enp39s0 weight 1
        nexthop via fe80::44 dev enp39s0 weight 1

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>
Reviewed-by: Andrea Claudi <aclaudi@redhat.com>
Acked-by: Roopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>