libbinder: 'RpcSession::addIncomingConnection'

Factor out complex bit of logic to setup an incoming connection into a
new function, in preparation for being able to set up the connection in
a different way.

Bug: 193801719
Test: binderRpcTest
Change-Id: I09a4520a5f00bb658c864000f7861a687a47efb0
2 files changed