Meta server: implement append chunk allocation handling of RPCs with different short and log RPC formats for the same cached chunk entry by reusing response string only in the case if cached RPC response string format matches request's format. Get rid of redundant "master" member in allocate RPC, which corresponds to the front element of the "servers" array. Change append cache to store all servers, instead of only master, in order to allow to handle RPCs with short and long RPCs formats for the same cached chunk append entry.