Prepare key_value storage for RB split
Prepare key_value storage for RB split

Change-Id: I55d9cc893519a095fc378d2890cb7ccb72ae0d59

milimetric/restbase,d00rman/restbase,Pchelolo/restbase,cscott/restbase,wikimedia/mediawiki-services-restbase,wikimedia/restbase,wikimedia/mediawiki-services-restbase,Pchelolo/restbase,cscott/restbase,d00rman/restbase,wikimedia/restbase,milimetric/restbase