Switch to decorators.idempotent_id on network

So many modules are using test.idempotent_id and this is for
switching to decorators.idempotent_id on network.

Change-Id: I2735d04dfbd5d48e87894457f2fc1172edf4da44
Related-Bug: #1616913
diff --git a/tempest/api/network/admin/test_quotas.py b/tempest/api/network/admin/test_quotas.py
index 8695ebd..7b6ebef 100644
--- a/tempest/api/network/admin/test_quotas.py
+++ b/tempest/api/network/admin/test_quotas.py
@@ -16,6 +16,7 @@
 from tempest.api.network import base
 from tempest.common.utils import data_utils
 from tempest.lib.common.utils import test_utils
+from tempest.lib import decorators
 from tempest import test
 
 
@@ -78,7 +79,7 @@
         for q in non_default_quotas['quotas']:
             self.assertNotEqual(project_id, q['tenant_id'])
 
-    @test.idempotent_id('2390f766-836d-40ef-9aeb-e810d78207fb')
+    @decorators.idempotent_id('2390f766-836d-40ef-9aeb-e810d78207fb')
     def test_quotas(self):
         new_quotas = {'network': 0, 'port': 0}
         self._check_quotas(new_quotas)