'Shut down a list of OVS switches'

@classmethod
def batchShutdown(cls, switches, run=errRun):

    delcmd = 'del-br    %s'
    if (switches and (not switches[0].isOldOVS())):
        delcmd = ('--if-exists    ' + delcmd)
    run(('ovs-vsctl    ' + '    --    '.join(((delcmd % s) for s in switches))))
    pids = '    '.join((str(switch.pid) for switch in switches))
    run(('kill    -HUP    ' + pids))
    for switch in switches:
        switch.shell = None
    return switches
