Fix the dispatcher not being threadsafe

Fix the dispatcher not being threadsafe

It turns out that the createServer/createClient calls actually need a
initializer which is protocol-specific and that listener needs to be
more than an abstract method, as there is protocol-specific state which
needs to be maintained.

Change-Id: Ia70c01183b23f79f7f1d8376cbe04c6af2f549d1
Signed-off-by: Robert Varga <rovarga@cisco.com>