BugLink: http://bugs.launchpad.net/bugs/1670508

This will allow us to do protocol specific tranformations of packets
before sending to the server. For SMB3 it can be used to support
encryption.
Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
(cherry picked from commit 7fb8986e)
Signed-off-by: Joseph Salisbury <joseph.salisbury@canonical.com>