Removes deprecated net_common module

Module net_common was replaced by module net_resources as part of migration of
scenario tests to tempest clients.
This patch fixes a few rogue references and removes this module completely.

Change-Id: I5426e030895d219ac456b3cceb361675c839b876
Partially-implements: bp/tempest-client-scenarios
diff --git a/tempest/scenario/manager.py b/tempest/scenario/manager.py
index 93712fc..b3b4fbf 100644
--- a/tempest/scenario/manager.py
+++ b/tempest/scenario/manager.py
@@ -21,7 +21,6 @@
 import netaddr
 import six
 
-from tempest.api.network import common as net_common
 from tempest import auth
 from tempest import clients
 from tempest.common import debug
@@ -590,7 +589,7 @@
 
     def _get_network_by_name(self, network_name):
         net = self._list_networks(name=network_name)
-        return net_common.AttributeDict(net[0])
+        return net_resources.AttributeDict(net[0])
 
     def _create_floating_ip(self, thing, external_network_id, port_id=None,
                             client=None):