helper/proc: raise FulfillmentTimeout in tests

This appears to be yet another source of spurious test failures.

Signed-off-by: Ophestra <cat@gensokyo.uk>

helper/proc/files.go

@@ -6,11 +6,18 @@ import (
 	"os/exec"
 	"sync/atomic"
 	"syscall"
+	"testing"
 	"time"
 )
 
 var FulfillmentTimeout = 2 * time.Second
 
+func init() {
+	if testing.Testing() {
+		FulfillmentTimeout *= 10
+	}
+}
+
 // A File is an extra file with deferred initialisation.
 type File interface {
 	// Init initialises File state. Init must not be called more than once.