Remove the concept of a root dir out of engine

This makes the engine more general purpose so that we can
use it and the job routing functionality for reexec'ing our binary
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)

Conflicts:
	integration/runtime_test.go

integration/runtime_test.go

@@ -627,10 +627,9 @@ func TestRestore(t *testing.T) {
 
 	// Here are are simulating a docker restart - that is, reloading all containers
 	// from scratch
-	eng = newTestEngine(t, false, eng.Root())
-	daemon2 := mkDaemonFromEngine(eng, t)
-	if len(daemon2.List()) != 2 {
-		t.Errorf("Expected 2 container, %v found", len(daemon2.List()))
+	eng = newTestEngine(t, false, runtime.Config().Root)
+	if len(runtime2.List()) != 2 {
+		t.Errorf("Expected 2 container, %v found", len(runtime2.List()))
 	}
 	runningCount := 0
 	for _, c := range daemon2.List() {

integration/server_test.go

@@ -149,7 +149,7 @@ func TestRestartKillWait(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	eng = newTestEngine(t, false, eng.Root())
+	eng = newTestEngine(t, false, runtime.Config().Root)
 	srv = mkServerFromEngine(eng, t)
 
 	job = srv.Eng.Job("containers")

integration/utils_test.go

@@ -181,7 +181,7 @@ func newTestEngine(t utils.Fataler, autorestart bool, root string) *engine.Engin
 			root = dir
 		}
 	}
-	eng, err := engine.New(root)
+	eng, err := engine.New()
 	if err != nil {
 		t.Fatal(err)
 	}