Fix tempest_lib import order

tempest_lib is 3rd party library and it should be imported as the
second block. However the import is wrong in account_generator.
So this patch fixes the order.

Change-Id: Ib5ba5c35fba07d03c3c26bb84dca57931d1a1b63
diff --git a/tempest/cmd/account_generator.py b/tempest/cmd/account_generator.py
index 5a2713b..dabb4e8 100755
--- a/tempest/cmd/account_generator.py
+++ b/tempest/cmd/account_generator.py
@@ -87,6 +87,9 @@
 import os
 
 from oslo_log import log as logging
+import tempest_lib.auth
+from tempest_lib.common.utils import data_utils
+import tempest_lib.exceptions
 import yaml
 
 from tempest.common import identity
@@ -98,9 +101,6 @@
 from tempest.services.network.json import network_client
 from tempest.services.network.json import networks_client
 from tempest.services.network.json import subnets_client
-import tempest_lib.auth
-from tempest_lib.common.utils import data_utils
-import tempest_lib.exceptions
 
 LOG = None
 CONF = config.CONF