Added Exists, CreateIfNotExists, and DeleteIfExists to Data Lake#9996

seanmcc-msft merged 2 commits intoAzure:masterAzure/azure-sdk-for-net:masterfrom

seanmcc-msft:feature/storage/dataLakeExists2seanmcc-msft/azure-sdk-for-net:feature/storage/dataLakeExists2Copy head branch name to clipboard