[2.0.1RN]REST API for flush requires admin credentials while it makes sense to allow it with bucket credentials

SUBJ.

Matt convinced me that indeed we did it wrong:

<alkby> I believe 1.7 and 1.6 always demanded admin
<alkby> and 1.8 too
<ingenthr> that's a real problem from a client perspective, since someone using a client is just using a bucket
<alkby> right but flush is a very destructive operation
<ingenthr> if buckets are in fact about multitenancy, then the tenant should be able to throw away their contents
<ingenthr> yep, I know. :)
<alkby> for unit tests you set it up for bucket with admin credentials
<alkby> well, tenant is good argument
<ingenthr> this means it's not functionally equivalent to memcached flush though, and that was the whole point of MB-5170
<ingenthr> that we couldn't do memcached flush safely, so we'd replace it with RESTful flush
<alkby> you're right
<alkby> lets file a bug and address it asap. Thanks for raising this
<ingenthr> but if restful flush is different semantically (you can flush this only with super creds)
<ingenthr> okay, will do, thanks
<alkby> I'll file bug