Blob DB: Fix GC handling for inlined blob
Blob DB: Fix GC handling for inlined blob

Summary:
Garbage collection checks if the offset in blob index matches the offset of the blob value in the file. If it is a mismatch, the value is the current version. However it failed to check if the blob index is an inlined type, which don't even have an offset. Fixing it.
Closes https://github.com/facebook/rocksdb/pull/3194

Differential Revision: D6394270

Pulled By: yiwu-arbug

fbshipit-source-id: 7c2b9d795f1116f55f4d728086980f9b6e88ea78

SunguckLee/RocksDB,SunguckLee/RocksDB,SunguckLee/RocksDB,SunguckLee/RocksDB,SunguckLee/RocksDB,SunguckLee/RocksDB,SunguckLee/RocksDB,SunguckLee/RocksDB