MB-100: rem depricated wait_for_replication from rest_client

correct implementation is in rebalance_helper
+ common code style in rest_client

Change-Id: I467ef3e4d239c0d9de69ca247b0920bbce3599cc
Reviewed-on: http://review.couchbase.org/23771
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>