linear iterator: fix bz2 iteration (#9)

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### Description

For bags with bz2 compression that are not indexed, the linear iterator
mistakenly fails too early with EOF. This is because we weren't
resetting `inChunk` for bz2 bags only.

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linear_iterator.go

@@ -94,6 +94,7 @@ func (it *linearIterator) Next() (*Connection, *Message, error) {
 				continue
 			case CompressionBZ2:
 				it.reader.Reset(bzip2.NewReader(bytes.NewReader(chunkData)))
+				it.inChunk = true
 			default:
 				return nil, nil, ErrUnsupportedCompression{string(compression)}
 			}