Replicaset's call method

[Talkytitan5127]

• add feature "Call method of Replicaset" - provide means for make map-reduce read requests
• correct DiscoveryAllBuckets - totalBucketCount less than batch count then tt returns 0 in nextFrom, in this case methods goes in endless cycle
• add test with running tarantool instance

[KaymeKaydex]

Hi! Thanks for the nice patch! I noted a few lines that raised questions for me. But the main question is about the possible applications of this method. However, the testing code looks amazing, I will definitely run it soon and see how it works