Support the "order" key in "update_config" for compose

Signed-off-by: Antonis Kalipetis <akalipetis@gmail.com>

cli/compose/loader/full-example.yml

@@ -31,6 +31,7 @@ services:
         failure_action: continue
         monitor: 60s
         max_failure_ratio: 0.3
+        order: start-first
       resources:
         limits:
           cpus: '0.001'

cli/compose/loader/loader_test.go

@@ -687,6 +687,7 @@ func TestFullExample(t *testing.T) {
 				FailureAction:   "continue",
 				Monitor:         time.Duration(60 * time.Second),
 				MaxFailureRatio: 0.3,
+				Order:           "start-first",
 			},
 			Resources: types.Resources{
 				Limits: &types.Resource{