Skip test_subnet_details slow test until bug 1813198 is fixed

The bug is killing throughput in our CI system [1] so until it's
fixed I'm proposing that we skip it.

http://status.openstack.org/elastic-recheck/#1813198
http://status.openstack.org/elastic-recheck/gate.html#1813198

Change-Id: I1a6f35dcb15110297cd491b902d7a8279861997e
Related-Bug: #1813198
diff --git a/tempest/scenario/test_network_basic_ops.py b/tempest/scenario/test_network_basic_ops.py
index c11070c..a473cc9 100644
--- a/tempest/scenario/test_network_basic_ops.py
+++ b/tempest/scenario/test_network_basic_ops.py
@@ -544,6 +544,7 @@
             should_connect=True, msg="after updating "
             "admin_state_up of router to True")
 
+    @decorators.skip_because(bug='1813198')
     @decorators.idempotent_id('d8bb918e-e2df-48b2-97cd-b73c95450980')
     @testtools.skipIf(CONF.network.shared_physical_network,
                       'network isolation not available')