Drop socket manager multi service support

Drop socket manager multi service support

That feature has never been used, it's always been dead weight.
Security manager is a single service so that's unlikely to ever change.

Implications:
* no need to store/check interface ID
* one service per socket manager - less bookkeeping, simpler destructor
* socket descriptors now only apply to accepted sockets

Change-Id: I84ce915f0ff6929df45a40a0a8f5cbf7a4214694