sysctl.d: request ECN on both in and outgoing connections

sysctl.d: request ECN on both in and outgoing connections

To further avoid bufferbloat Explicit Congestion Notification (ECN)
should be enabled for both in and outgoing connections. The kernel
default is to enable it when requested for incoming connections, but
not to request it on outgoing connections. This patch enables it for
both.

A long time ago enabling these was causing problems, but these issues
have since been dealt with.

For issue #9087