MB-9984 Fix recovery with star replication topology.

When starting recovery we create a special bucket config whose map
contains chains like [undefined, Node] when we want to create the
replica vbucket on Node. The problem was that
janitor_agent:apply_new_bucket_config_new_style_star used
ns_bucket:map_to_replicas_star to decide on which nodes replica
vbuckets have to be created. And the latter function explicitly
ignores replication pairs where either master or replica is undefined.

Change-Id: I558d63b3949a49edda8d2e8751c4f448fb203204
Reviewed-on: http://review.couchbase.org/32746
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>