Use oslo.utils

Module `importutils` from common code was graduated to oslo.utils,
so it would be great if we reuse this library.
Remove unused strutils.py and gettextutils.py

Change-Id: Iaae19fc5018d83103e5f15ff76d6da686bfdf5f8

Author: ochuprykov

openstack-common.conf

@@ -1,10 +1,7 @@
 [DEFAULT]
 
 # The list of modules to copy from openstack-common
-module=gettextutils
 module=install_venv_common
-module=importutils
-module=strutils
 
 # The base module to hold the copy of openstack.common
 base=openstackclient

openstackclient/common/utils.py

@@ -21,8 +21,9 @@
 import six
 import time
 
+from oslo.utils import importutils
+
 from openstackclient.common import exceptions
-from openstackclient.openstack.common import importutils
 
 
 def find_resource(manager, name_or_id):