net: tcp: Enable active connection support by default

Application can by default do a connection request. If this is
not needed (app is only working in server role i.e., only
listening connection attempts), then some memory can be saved
by disabling client role support.

Change-Id: I33ed95ad0cf099a70563465beff555ec4adab958
Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>