bgpd: EVPN crash because of incorrect nexthop for IPv6 prefix

bgpd: EVPN crash because of incorrect nexthop for IPv6 prefix

RCA:
When we install IPv6 prefix imported from EVPN RT-5 in vrf, nexthop of the IPv6
route should be IPv4 mapped IPv6 address. In function
install_evpn_route_entry_in_vrf, we generate a new attribute with IPv4 mapped
IPv6 nexthop, but we use parent->attr while creating the actual route.
Thus, Ipv4 nexthop is assigned to this route.
Because of this incorrect nexthop, we observed a crash in function
update_ipv6nh_for_route_install.

Fix:
Pass the new attribute with Ipv4 mapped Ipv6 nexthop to
bgp_create_evpn_bgp_path_info

Signed-off-by: Ameya Dharkar <adharkar@vmware.com>