fib: make sure dpo is valid even when path pool expands
fib: make sure dpo is valid even when path pool expands

The path pool can expand during in fib_path_attached_next_hop_get_adj()
when calling adj_nbr_add_or_lock(). If dpo points to a path->fp_dpo, its
reference becomes stale.
Use a temporary copy instead.

Type: fix

Change-Id: Ie966cb5f3f7b416425964dca12f1f586bfc2010c
Signed-off-by: Benoît Ganne <38aad8ffcfa407b890d258e568f161530f66882d@cisco.com>

FDio/vpp,FDio/vpp,FDio/vpp,chrisy/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,chrisy/vpp