Catch BadRequest exception from correct module

Catch the correct BadRequest exception from the neutron
client module so deployments that don't support overlapping
IP addresses can be tested.

Change-Id: Ica58ffbff6cedd362e2b2b807438ec61bddf2f25
Closes-Bug: #1359508
diff --git a/tempest/common/isolated_creds.py b/tempest/common/isolated_creds.py
index f711f2f..712a892 100644
--- a/tempest/common/isolated_creds.py
+++ b/tempest/common/isolated_creds.py
@@ -13,6 +13,7 @@
 #    under the License.
 
 import netaddr
+from neutronclient.common import exceptions as n_exc
 
 from tempest import auth
 from tempest import clients
@@ -261,7 +262,7 @@
                     body['subnet']['cidr'] = str(subnet_cidr)
                     resp_body = self.network_admin_client.create_subnet(body)
                 break
-            except exceptions.BadRequest as e:
+            except (n_exc.BadRequest, exceptions.BadRequest) as e:
                 if 'overlaps with another subnet' not in str(e):
                     raise
         else: