client: Get and GetRange handlers miss some invalid messages sequences

[cthulhu-rider]

Get(Range) response payload is defined as oneof, but messages must be streamed in a strict order:

• all messages with chunk or
• exactly one message with split_info field

Current Behavior

1. split_info after chunk -> split info error (Range)
2. chunk after split_info -> split info error

Expected Behavior

1. unexpected message instead of chunk part: *object.SplitInfo error
2. unexpected message after split info response error

Steps to Reproduce

• corresponding tests from Test coverage for Client ops #641

Regression

no

Your Environment

• Version of the product used: 335d9fe