Enhance logic to populate BlobId data type correctly when simple blob is exactly max_chunk bytes

[lightningrob]

This is a follow-on to #940 where the BlobId flag was enhanced to include BlobDataType with three possible values:

• MetaData (composite blob)
• Simple (self-contained data blob)
• DataChunk (chunk that is part of a Composite blob)

The initial implementation, due to sequencing and asynchronicity, does not handle the case where a simple blob's size is exactly the configured chunking limit. This issue is filed to track the needed enhancement.