feat(cli): make -no-<bool_flag_name> option when boolean default is True

[ocervell]

We might want to define default boolean flags to True like:

class nmap(VulnMulti):
  opts = {
    # 'tcp_connect': {'type': bool, 'short': 'sT', 'default': False, 'help': 'TCP Connect scan'},
  }

and being able to disable them would required the opposite flag --no-tcp-connect or --no-sT.