fix cbbackup_restore.flush_buckets
fix cbbackup_restore.flush_buckets

Change-Id: I459faae74e5b7dec3a2ab0ac11c6e7fd226338ac
Reviewed-on: http://review.couchbase.org/57762
Well-Formed: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Andrei Baranouski <f6b50d8f3f8d6abadc89468769320bb7ef9099f0@gmail.com>
Tested-by: Andrei Baranouski <f6b50d8f3f8d6abadc89468769320bb7ef9099f0@gmail.com>

dkao-cb/perfrunner,pavel-paulau/perfrunner,pavel-paulau/perfrunner,couchbase/perfrunner,EricACooper/perfrunner,pavel-paulau/perfrunner,EricACooper/perfrunner,couchbase/perfrunner,EricACooper/perfrunner,pavel-paulau/perfrunner,dkao-cb/perfrunner,couchbase/perfrunner,couchbase/perfrunner,pavel-paulau/perfrunner,couchbase/perfrunner,couchbase/perfrunner,EricACooper/perfrunner