S3 authentication via IAM profiles

[robholland]

It doesn't seem that objstorage supports IAM instance profiles. With deis workflow v2.5.0 installed via helmc dockerbuilder fails with an access denied message from S3 when trying to deploy via git:

https://github.com/deis/dockerbuilder/blob/master/rootfs/deploy.py#L91

The tar file it is trying to download had been successfully uploaded to the bucket, so the S3 IAM profile system is working elsewhere in deis.

[kmala]

this should be working as per me...can you say what your object secret is kubectl --namespace=deis describe secret objectstorage-keyfile

[robholland]

I've now changed it to add credentials, but it had region, builder-bucket, database-bucket, registry-bucket all set, and "accesskey: null", "secretkey: null".

Now that I've set accesskey and secretkey (leaving the other settings unchanged) and everything is working as intended. Previously some parts of deis worked but dockerbuilder didn't.