ssa.c: In ssa_downstream_listen, fix case when listen rsock already setup

This occurs in core/plugin.

Signed-off-by: Hal Rosenstock <hal@mellanox.com>
distrib/Makefile.am: Added commented out line for core integration

access <-> core CFLAGS line is commented out
ACM <-> access CFLAGS line is still active

Signed-off-by: Hal Rosenstock <hal@mellanox.com>