Change log for unknown mt to debug
Change log for unknown mt to debug

This log message shows up in the client's logs. For any media type that
the client doesn't know about it will wind up with a warning log.
Downgrade this to debug since it is more of a development concern.

We encountered this trying to fetch Docker plugins which has a media
type for plugin configs.

Signed-off-by: Brian Goff <dc73d0991b982a8303e713ef531a313af77e242a@gmail.com>

vdemeester/containerd,mikebrow/containerd,estesp/containerd,thaJeztah/containerd,vdemeester/containerd,containerd/containerd,containerd/containerd,thaJeztah/containerd,estesp/containerd,mikebrow/containerd,dmcgowan/containerd,dmcgowan/containerd