Support ENXIO on lx-branded zones

[geek]

Related to TritonDataCenter/sdc-docker#91

ENXIO is returned on illumos by ioctl, which gets called by tcsetgrp. This occurs when using tini inside a docker container running on lx-branded zones on illumos.

Here are a couple of docker images to help prove this out:
Before fix: d0cker/test-dtrace:1.1.1
After fix: d0cker/test-dtrace:1.1.2

With d0cker/test-dtrace:1.1.1 image:

[INFO  tini (1)] Spawned child process 'node' with pid '52187'
[FATAL tini (52187)] tcsetpgrp failed: No such device or address
[DEBUG tini (1)] Received SIGCHLD
[DEBUG tini (1)] Reaped child with pid: '52187'
[INFO  tini (1)] Main child exited normally (with status '1')
[TRACE tini (1)] No child to wait
[TRACE tini (1)] Exiting: child has exited

With d0cker/test-dtrace:1.1.2 image:

[INFO  tini (1)] Spawned child process 'node' with pid '28463'
[DEBUG tini (28463)] gpid: 27999
Listening at http://localhost:8080

[krallin]

Thanks @geek, this is great!

There's a little typo in here but I'll fix in a separate commit; should I add you to the contributor list as well?

Cheers,

[geek]

@krallin yes please!

[krallin]

Done 😄