Avoid creating tables when we load AVRO files (#620)
Avoid creating tables when we load AVRO files (#620)

In the current implementation, we create partitioned tables using `bq mk table ...` command before we load AVRO files. Thus we need to ensure table exists befor we start loading AVRO file into it.

Note, if we resolve issue #582 adding `create_disposition` flag would not be needed.
googlegenomics/gcp-variant-transforms,googlegenomics/gcp-variant-transforms