Fix direct datastore assignments to pass msftidy

This patch should allow ```rport``` and ```smbdirect``` to be modified at runtime without touching the actual datastore options.

 - [ ] Test the module against a Windows SMB service
True, but that is a different module.  Pperhaps I am misreading this, but as currently in master:

```
 # Fingerprint a single host
  def run_host(ip)

    [[139, false], [445, true]].each do |info|

    @rport = info[0]
    @smbdirect = info[1]
```

For the module in this PR, you can set RPORT but it is not used.  


```
msf auxiliary(smb_enumusers) >  set RPORT 12345
RPORT => 12345
msf auxiliary(smb_enumusers) > run

[*] 10.4.24.54 SPIDER-WXP [ Administrator, ASPNET, Guest, HelpAssistant, sshd, SUPPORT_388945a0 ] ( LockoutTries=0 PasswordMin=0 )
[*] Scanned 1 of 1 hosts (100% complete)
[*] Auxiliary module execution completed
```

That host definitely is not listening on 12345/TCP.