1. Fix client not reading all server addresses in READ response
The metadata server sends address info for ALL chunk servers holding
a chunk, but the client only read info for ONE server. This caused
message parsing to become misaligned for subsequent chunks.
Added a loop to iterate through all num_servers and read each
server's address list (using the first one, skipping the rest).
2. Fix tag value conflict between metadata and chunk server responses
TAG_RETRIEVE_METADATA_FOR_READ was 1, which conflicted with chunk
download range indices (0, 1, 2, 3...). When the second chunk
download response came with range_idx=1, it was incorrectly treated
as a metadata response.
Changed TAG values from positive to negative integers since range
indices are always non-negative.
Also updated the test to properly exit on success instead of assert(0).
https://claude.ai/code/session_01QYDQCNiUj1cjrsS6qRgkvd