unix: enable TestPassFD on AIX 7.2 TL >= 2
unix: enable TestPassFD on AIX 7.2 TL >= 2

Follow CL 171339 and enable TestPassFD for AIX 7.2 TL >= 2

Change-Id: Icf781798a6f9fe99a57c23bc7f7e7c1361bdcec2
Reviewed-on: https://go-review.googlesource.com/c/sys/+/171941
Run-TryBot: Tobias Klauser <0a68dd4915066ec5d3f81f75a828fee53dcc8822@gmail.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/sys,multiplay/golang-sys,multiplay/golang-sys,multiplay/golang-sys,golang/sys,golang/sys,multiplay/golang-sys