dbus/socket: catch and document ETOOMANYREFS
dbus/socket: catch and document ETOOMANYREFS

Add a comment to sendmmsg() regarding ETOOMANYREFS. Our solution
depends on the upstream discussion regarding dropping "recursion_level"
on UDS. Until then, we just employ a hack that penalizes the
destination of such FDs.

Signed-off-by: David Herrmann <fb53b2ddb8d141e0cb39d7c67c2f81b6bc2eb0f7@gmail.com>

bus1/dbus-broker