MB-9007: use different variables for RemoteBucket

When vb replicator inits, it call remote_cluster_info multiple
times to fetch the remote bucket and remote vbucket info. In
particular we call remote_clusters_info:get_remote_bucket_by_ref()
to get the remote_bucket, and get_memcached_vbucket_info_by_ref()
to get ip, port and remote_bucket. However, in some cases the
remote_bucket returned by these two functions may not be exactly
the same if it is updated between the two calls, causing badmatch
Erlang error when vb replicator initializes.

The fix is simple, we just use different variables for the
remote_bucket returned by these two calls.

Change-Id: If44f7124059bea85aade2051e619371aa93fbc91
Reviewed-on: http://review.couchbase.org/28687
Tested-by: Junyi Xie <junyi.couchbase@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>