API tests: Check MTU sanity of trunk/subport

The MTU of VLAN subinterfaces must not be greater than
MTU of the trunk port. This commit adds API tests that
check that API follows theses guidelines

Change-Id: Ib40c4d44a97b6c9183d48e79383d88dbf2c952db
Partially-Implements: blueprint vlan-aware-vms
diff --git a/neutron/tests/tempest/config.py b/neutron/tests/tempest/config.py
index f50fa39..479d909 100644
--- a/neutron/tests/tempest/config.py
+++ b/neutron/tests/tempest/config.py
@@ -22,7 +22,12 @@
     cfg.BoolOpt('specify_floating_ip_address_available',
                 default=True,
                 help='Allow passing an IP Address of the floating ip when '
-                     'creating the floating ip')]
+                     'creating the floating ip'),
+    cfg.ListOpt('available_type_drivers',
+                default=[],
+                help='List of network types available to neutron, '
+                     'e.g. vxlan,vlan,gre.'),
+]
 
 # TODO(amuller): Redo configuration options registration as part of the planned
 # transition to the Tempest plugin architecture