The attach API used to always return the Content-Type
`vnd.docker.raw-stream`, however docker api v1.42 added the
`vnd.docker.multiplexed-stream` type when no tty was used.
Follow suit and return the same header for docker api v1.42 and libpod
v4.7.0. This technically allows clients to make a small optimization as
they no longer need to inspect the container to see if they get a raw or
multiplexed stream.
Signed-off-by: Paul Holzinger <pholzing@redhat.com>
Paul Holzinger
7c9c969815