Workaround: add default dpopts='--no-slicing' to UserSwitch
Workaround: add default dpopts='--no-slicing' to UserSwitch

This disables slicing by default but fixes bandwidth limits.
Eventually we want to enable both to work together, but for now
this enables one or the other depending on the dpopts setting.

mininet/mininet,mininet/mininet,mininet/mininet