support batching of ip route get commands

support batching of ip route get commands

This patch replaces exits with returns in
ip route get command handling. This allows batching
of ip route get commands.

$cat route_get_batch.txt
route get 10.0.14.2
route get 12.0.14.2
route get 10.0.14.4

$ip -batch route_get_batch.txt
local 10.0.14.2 dev lo  src 10.0.14.2
    cache <local>
12.0.14.2 via 192.168.0.2 dev eth0  src 192.168.0.15
    cache
10.0.14.4 dev dummy0  src 10.0.14.2
    cache

Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>