MB-100 Remove unused predicate parameter.

Change-Id: I7a8c5e6c61c3958926e141fb45f1e7fb144383b6
Reviewed-on: http://review.couchbase.org/28866
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
MB-100 Factor out node status check into a dedicated function.

Additionally, I changed the way absence of active_buckets key is
handled. Previously we just used empty list as a default. But this
means that for the case of bucket deletion we would decide that the
node successfully deleted bucket when it's not really the case.

Change-Id: I6b0273243046c559b4e5cd0b9fa0a76379c02819
Reviewed-on: http://review.couchbase.org/28867
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>