same nh index  is allocated for multiple composite nexthops
same nh index  is allocated for multiple composite nexthops

in current logic, nexthop is allocated from resource manager from
keys<nhid, label>derived from compositenhkey, this is done by iterating
component nh key list , populate <nhid, label> only if key is not NULL,
but this can create a scenario where two composite NH end up getting same index
for the following combination
composie NH1 : component NH keys NULL,B,C  (one Key is NULL because of deletion of component nh)
composite NH2: component nh keys B,C
Since we are skipping NULL component keys, same set of keys are derived
from both composite NHs

Fix:
for inactive component NH, we are populating <nh_id, label> to 0,
applying the same logic for NULL key case as well to make it
unique key combination

Change-Id: I5a78b64cb346ae934746eb78bd6eb9f695de76dc
Closes-Bug: #1760960

eonpatapon/contrail-controller,eonpatapon/contrail-controller,rombie/contrail-controller,eonpatapon/contrail-controller,rombie/contrail-controller,rombie/contrail-controller,eonpatapon/contrail-controller,rombie/contrail-controller,eonpatapon/contrail-controller,eonpatapon/contrail-controller,rombie/contrail-controller,eonpatapon/contrail-controller,rombie/contrail-controller,rombie/contrail-controller