Skip test_list_network_filter_provider_attributes when no provider_vlans

When no provider VLAN networks have been configured,
test_list_network_filter_provider_attributes has to be skipped.

This test was added recently [1] and it assumes some provider_vlans are
always configured, but that is not the case (default value is []).

[1] https://review.opendev.org/c/openstack/neutron-tempest-plugin/+/949975

Related-Bug: #2109354
Change-Id: Icde987373202d084d5771456739985a709af3241
Signed-off-by: Eduardo Olivares <eolivare@redhat.com>
diff --git a/neutron_tempest_plugin/api/admin/test_networks.py b/neutron_tempest_plugin/api/admin/test_networks.py
index ea867d1..a67afa3 100644
--- a/neutron_tempest_plugin/api/admin/test_networks.py
+++ b/neutron_tempest_plugin/api/admin/test_networks.py
@@ -89,6 +89,8 @@
 
     @decorators.idempotent_id('bbb9a2be-c9a7-4693-ac8e-d51b5371b68d')
     def test_list_network_filter_provider_attributes(self):
+        if not config.CONF.neutron_plugin_options.provider_vlans:
+            raise self.skipException("No provider VLAN networks available")
         project_id = self.client.project_id
         physnet_name = config.CONF.neutron_plugin_options.provider_vlans[0]
         # Check project networks pre-created.