cmd/unix/reverse_awk spins CPU after user exit

[egypt]

While testing payloads for #14509 I noticed cmd/unix/reverse_awk spins CPU after user exit.

Steps to reproduce

• use payload/cmd/unix/reverse_awk
• generate -f raw
• copy the command
• to_handler
• paste the command into a terminal somewhere
• interact with the session: sessions -1
• id or something to make sure it's real
• exit or ctrl-c
• see the session close

Expected behavior

clean exit

Current behavior

If you exit, the payload continues to call back. If you ctrl-c, it doesn't call back anymore but the process is still there. Either way, my fan spins up

Metasploit version

Tested in #14509 as mentioned. Verified that the same issue exists on current master, 7b31d33

[bcoles]

Welp. Likely introduced by #10035 to fix #9750. Context: #9750 (comment)

[timwr]

I can grab this, looks straightforward