Spark submit should ignore cache for SNAPSHOT dependencies

When spark-submit is executed with --packages, it will not download the dependency jars when they are available in cache (e.g. ivy cache), even when the dependencies are SNAPSHOTs.

This might block developers who work on external modules in Spark (e.g. spark-avro), since they need to remove the cache manually every time when they update the code during developments (which generates SNAPSHOT jars). Without knowing this, they could be blocked wondering why their code changes are not reflected in spark-submit executions.