[bt][data] SocketFactory: remove a template argument

Having removed ChannelIdT from SocketChannelRelay, we can
remove ChannelIdT from SocketFactory as well. Make it so.

Bug: NET-1932
Test: bt-host-unittests (on eve)

Change-Id: Idb2502e0d8269332a3fb4b5c557192b8551dbe6a
7 files changed