* Update redis.go
If the dgst key does not exist in the cache when calling HGET, `redis.String` will return an `ErrNil` which we need to translate into `distribution.ErrBlobUnknown` so that the error being returned can be properly handled. This will ensure that `SetDescriptor` is properly called from `cachedBlobStatter::Stat` for `repositoryScopedRedisBlobDescriptorService` which will update the redis cache and be considered as a Miss rather than an Error.
cc @manishtomar
* Update suite.go
Add unit test to ensure missing blobs for scoped repo properly return ErrBlobUnknown when HGET returns redis.ErrNil.
(cherry picked from commit dca6b9526a1d30dd218a9f321c4f84ecc4b5e62e)
Signed-off-by: Derek McGowan <derek@mcgstyle.net>
74d442a058