changed default value of getenvint to 0. fix tests

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)

engine/env.go

@@ -60,7 +60,7 @@ func (env *Env) GetInt64(key string) int64 {
 	s := strings.Trim(env.Get(key), " \t")
 	val, err := strconv.ParseInt(s, 10, 64)
 	if err != nil {
-		return -1
+		return 0
 	}
 	return val
 }

engine/env_test.go

@@ -62,7 +62,7 @@ func TestSetenvInt(t *testing.T) {
 	if val := job.GetenvInt("bar"); val != 42 {
 		t.Fatalf("GetenvInt returns incorrect value: %d", val)
 	}
-	if val := job.GetenvInt("nonexistent"); val != -1 {
+	if val := job.GetenvInt("nonexistent"); val != 0 {
 		t.Fatalf("GetenvInt returns incorrect value: %d", val)
 	}
 }