Added ovs-openflowd to list of zombies.
We may still need additional code to clean up after ovs.
Change import to reflect renamed mininet.term module.
Minor format tweaks.
Removed executability since mn -c is easier!
Make cleanup a param of mn, not a separate script
Also switch from print to info statements, to enable a non-verboseclean. Instead of 'mnclean', now run 'mn -c'.