Replace use of functools.wraps() with six.wraps()

In Python 2.7, functools.wraps() does not provide the '__wrapped__'
attribute. This attribute is used by
oslo_utils.reflection.get_signature() when getting the signature of a
function. If a function is decorated without the '__wrapped__'
attribute then the signature will be of the decorator rather than the
underlying function.

From the six documentation for six.wraps():
    This is exactly the functools.wraps() decorator, but it sets the
    __wrapped__ attribute on what it decorates as functools.wraps()
    does on Python versions after 3.2.

Change-Id: Ic1c3e27e1578c914a86a2faf694c72dfdbfbda18
diff --git a/ironic_tempest_plugin/services/baremetal/base.py b/ironic_tempest_plugin/services/baremetal/base.py
index 757a770..494c780 100644
--- a/ironic_tempest_plugin/services/baremetal/base.py
+++ b/ironic_tempest_plugin/services/baremetal/base.py
@@ -10,9 +10,9 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import functools
 
 from oslo_serialization import jsonutils as json
+import six
 from six.moves import http_client
 from six.moves.urllib import parse as urllib
 from tempest.lib.common import api_version_utils
@@ -36,7 +36,7 @@
 def handle_errors(f):
     """A decorator that allows to ignore certain types of errors."""
 
-    @functools.wraps(f)
+    @six.wraps(f)
     def wrapper(*args, **kwargs):
         param_name = 'ignore_errors'
         ignored_errors = kwargs.get(param_name, tuple())