Added support for identity auth in Azure driver

Added support for identity auth in Azure driver

Signed-off-by: Ruslan Gabitov <ruslan.gabitov@live.com>
Fix Azure driver with gofmt

Fix Azure driver with gofmt

Signed-off-by: Ruslan Gabitov <ruslan.gabitov@live.com>
Added comment to Azure driver

Added comment explaining retries in hackForIdentityAuth() method

Signed-off-by: Ruslan Gabitov <ruslan.gabitov@live.com>
Merge pull request #64 from MSOpenTech/master

Added support for identity auth in Azure driver