Add dummy driver

Added dummy driver for ease of testing and development of REST APIs
and internal manila interfaces.
It can be enabled as backend in the same way as all other share drivers.
But, it does not provide any resources.

Also, update tempest to be able to work with share-networks when
networks are defined via config and not API.

CI hooks are configured to run tempest twice using both available
driver modes. Where DHSS=True mode uses StandAloneNetworkPlugin as
network backend.

Change-Id: I9053dddfc643cb5a6602f15235b91bbaea727dbd
Implements BluePrint dummy-driver
diff --git a/manila_tempest_tests/config.py b/manila_tempest_tests/config.py
index 7a7ee6f..4b394c6 100644
--- a/manila_tempest_tests/config.py
+++ b/manila_tempest_tests/config.py
@@ -56,6 +56,15 @@
                 help="This option used to determine backend driver type, "
                      "multitenant driver uses share-networks, but "
                      "single-tenant doesn't."),
+    cfg.BoolOpt("create_networks_when_multitenancy_enabled",
+                default=True,
+                help="This option is used only when other "
+                     "'multitenancy_enabled' option is set to 'True'. "
+                     "If this one is set to True, then tempest will create "
+                     "neutron networks for each new manila share-network "
+                     "it creates. Else it will use manila share-networks with "
+                     "empty values (case of StandAloneNetworkPlugin and "
+                     "NeutronSingleNetworkPlugin)."),
     cfg.ListOpt("enable_protocols",
                 default=["nfs", "cifs"],
                 help="First value of list is protocol by default, "