Update the Redis dependency to use the last major production version.
The last version accepts a context parameter in all the network methods
so it allows us to pass it through them.
Change-Id: I34121b2ec3c2728602115c724933ad24c9e6e4fd
Move a specific interface & types used for testing to be a private
subpackage with a name that clearly identifies it for testing purpose.
Change-Id: I646cf3b6f0a3b518a6f9a125998dc5a02df02db6
