Remove qdisc_variants() function from functions.sh

qdisc_variants() used to set the explicit congestion notification (ecn)
attributes for (selected) ingress and egress leaf qdiscs.
Since setting of ECN has been moved to the GUI and can be modified
in fnctions.sh by setting the IECN and EECN variables, just delete the
function and the related variables ALLECN AUTOECN from functions.sh.
This fixes a spurious "sh: bad number" error that is visible when
/etc/init.d/sqm is used to start or stop the SQM system..