ip nexthop: Add space to display properly when showing a group

ip nexthop: Add space to display properly when showing a group

When displaying a nexthop group made up of other nexthops, the display
line shows this when you have additional data at the end:

id 42 group 43/44/45/46/47/48/49/50/51/52/53/54/55/56/57/58/59/60/61/62/63/64/65/66/67/68/69/70/71/72/73/74proto zebra

Modify code so that it shows:

id 42 group 43/44/45/46/47/48/49/50/51/52/53/54/55/56/57/58/59/60/61/62/63/64/65/66/67/68/69/70/71/72/73/74 proto zebra

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>