Remove dead code

Sir Codus Cleanupus vs. system.go

"This code doth offend me so" uttered Sir Codus Cleanupus
"and thus it must be cleft swiftly in twain". With one hefty
stroke of his broadsword he carved the old, unfunctioning
code in half and thus it ceased to be.

Signed-off-by: Dave Tucker <dt@docker.com>

libnetwork/system.go

@@ -1,34 +0,0 @@
-package libnetwork
-
-import (
-	"fmt"
-	"runtime"
-	"syscall"
-)
-
-// Via http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=7b21fddd087678a70ad64afc0f632e0f1071b092
-//
-// We need different setns values for the different platforms and arch
-// We are declaring the macro here because the SETNS syscall does not exist in th stdlib
-var setNsMap = map[string]uintptr{
-	"linux/386":     346,
-	"linux/amd64":   308,
-	"linux/arm":     374,
-	"linux/ppc64":   350,
-	"linux/ppc64le": 350,
-	"linux/s390x":   339,
-}
-
-func setns(fd uintptr, flags uintptr) error {
-	ns, exists := setNsMap[fmt.Sprintf("%s/%s", runtime.GOOS, runtime.GOARCH)]
-	if !exists {
-		return fmt.Errorf("unsupported platform %s/%s", runtime.GOOS, runtime.GOARCH)
-	}
-
-	_, _, err := syscall.RawSyscall(ns, fd, flags, 0)
-	if err != 0 {
-		return err
-	}
-
-	return nil
-}