internal/nettest: add AIX operating system

This commit adds AIX operating system to internal/nettest package.

It also disables unixpacket network.

Change-Id: Ie1a0b5c02d41ede7297c3706f6967be3438321a5
Reviewed-on: https://go-review.googlesource.com/c/144077Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

internal/nettest/helper_nobsd.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build linux solaris
+// +build aix linux solaris
 
 package nettest
 

internal/nettest/helper_posix.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin dragonfly freebsd linux netbsd openbsd solaris windows
+// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris windows
 
 package nettest
 

internal/nettest/helper_unix.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin dragonfly freebsd linux netbsd openbsd solaris
+// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
 
 package nettest
 

internal/nettest/stack.go

@@ -72,7 +72,7 @@ func TestableNetwork(network string) bool {
 		}
 	case "unixpacket":
 		switch runtime.GOOS {
-		case "android", "darwin", "freebsd", "js", "nacl", "plan9", "windows":
+		case "aix", "android", "darwin", "freebsd", "js", "nacl", "plan9", "windows":
 			return false
 		case "netbsd":
 			// It passes on amd64 at least. 386 fails (Issue 22927). arm is unknown.