--controller none crashes with VL2 topo (used remote instead) about mininet HOT 1 OPEN

@lantz I do not know what VL2 topology is and therefore if you find my arguments and questions below as offensive, I apologize for my ignorance.

Are you providing vl2 as a value to the --topo field ? I see in that case mininet will crash regardless of the value given to controller. That is because VL2 is an invalid topo name. Please see the ouptut below

sudo mn --topo VL2

Caught exception. Cleaning up...

Exception: Invalid topo name VL2

*** Removing excess controllers/ofprotocols/ofdatapaths/pings/noxes
killall controller ofprotocol ofdatapath ping nox_core lt-nox_core ovs-openflowd ovs-controller udpbwtest mnexec ivs 2> /dev/null
killall -9 controller ofprotocol ofdatapath ping nox_core lt-nox_core ovs-openflowd ovs-controller udpbwtest mnexec ivs 2> /dev/null
pkill -9 -f "sudo mnexec"
*** Removing junk from /tmp
rm -f /tmp/vconn* /tmp/vlogs* /tmp/.out /tmp/.log
*** Removing old X11 tunnels
*** Removing excess kernel datapaths
ps ax | egrep -o 'dp[0-9]+' | sed 's/dp/nl:/'
*** Removing OVS datapathsovs-vsctl --timeout=1 list-br
*** Removing all links of the pattern foo-ethX
ip link show | egrep -o '(\w+-eth\w+)'
*** Cleanup complete.

Do we wish to support vl2 topology in mininet ? If yes, should we use this issue for tracking the development of that ?

from mininet.