Updated to function with stack. Disallows identical vlans from file, and allows removal of multiple VLANs at one time.
Updated to function with stack. Disallows identical vlans from file, and
allows removal of multiple VLANs at one time.

nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome