[BlobGC] Remove adding of paths in file maintained for blob references

MarkSweepGarbageCollector also adds the path alongside the blob id in the references file which is maintained internally. For SharedDataStore cases this file is additionally uploaded to the datastore. Since, this file can become quite huge its better not to add the paths to this file and just log paths for GC. The node paths should still be added where available in #checkConsistency()