Fix Redmine 8291, sock_sendpage broken due to missing Bionic source

### Verification
- [x] On metasploitable, `echo 0 > /proc/sys/vm/mmap_min_addr`
- [x] Get a non-root shell on metasploitable
- [x] `use exploit/linux/local/sock_sendpage`, set a payload, set the session to your metasploitable shell
- [x] Verify: gets a new session, running as root