Allow application/octet-stream as a possible content-type (#999)
Allow application/octet-stream as a possible content-type (#999)

Due to eventual consistency of S3, sometimes the content type
returned by Minio S3 gateway doesn't match the value expected by
tests. This PR updates the test to allow application/octet-stream
as a possible value in addition to the expected content-type.

Fixes #997
harshavardhana/minio-go,minio/minio-go