zebra: Fix connected route deletion when multiple entry exists

zebra: Fix connected route deletion when multiple entry exists

When multiple interfaces have addresses in the same network, deleting
one of them may cause the wrong connected route being deleted.
For example:

    ip link add veth1 type veth peer veth2
    ip link set veth1 up
    ip link set veth2 up
    ip addr add dev veth1 192.168.0.1/24
    ip addr add dev veth2 192.168.0.2/24
    ip addr flush dev veth1

Zebra deletes the route of interface veth2 rather than veth1.

Should match nexthop against ere->re_nhe instead of ere->re->nhe.

Signed-off-by: Xiao Liang <shaw.leon@gmail.com>
(cherry picked from commit a35ba7ba602f87390cc9cbce3f0ceb61977f0949)