Background operation (media scan and media optimize) RANGE scope

permission enforcement:

1. Start key and end key must be within the same scope and has Range
role for the scope. The start key and end key must have the same prefix:
 
The byte array value of (0, offset+scopeValue.size()) must be equal for
start and end keys.

2. See the protocol definition for ACL.Scope for empty endkey
specification:

https://github.com/Seagate/kinetic-protocol/blob/master/kinetic.proto