Fix undefined method `rport' for the check command

So this PR is for the following issue:
https://dev.metasploit.com/redmine/issues/8783

So apparently when a module has RPORT, it doesn't necessarily have RPORT to go with it. bailiwicked_host.rb is an example.

To test, here's how:

- [ ] Run module auxiliary/spoof/dns/bailiwicked_host, set a fake RHOST to run it.
- [ ] There shouldn't be an error like in: https://community.rapid7.com/thread/4505
- [ ] Do another test with ms08_067_netapi, make sure the check command is still functioning properly.

Since I find the the design of "check" is kind of inconsistent (for example: normally when there's RHOST, there should be RPORT too, but not always), so if you can think of other things to test, please go for it.