avro schema conversion may fail with name conflict when using fixed types

Generating an avro schema from parquet may result in an error when using fixed length byte arrays.

For instance, if a parquet message type contains several repeated fixed types, the following error will be thrown:
org.apache.avro.SchemaParseException: Can't redefine: array
This happens because the conversion redifines the avro fixed type based on a non unique field name.