Don't log stack trace on S3/EC2 client errors.

Not all configurations of OpenStack have the EC2/S3 API's
enabled. For that matter the S3 "API" in Nova (object-store)
isn't even production ready. As such it would be really nice to
hide exceptions if the S3 and EC2 clients in Tempest can't be
configured.

Change-Id: I584c79ae3f00a215d26178002c686af2ac517c7e
diff --git a/tempest/tests/boto/__init__.py b/tempest/tests/boto/__init__.py
index 3d5ea6c..11fa077 100644
--- a/tempest/tests/boto/__init__.py
+++ b/tempest/tests/boto/__init__.py
@@ -73,7 +73,6 @@
         EC2_CAN_CONNECT_ERROR = "AWS credentials not set," +\
                                 " faild to get them even by keystoneclient"
     except Exception as exc:
-        logging.exception(exc)
         EC2_CAN_CONNECT_ERROR = str(exc)
     else:
         EC2_CAN_CONNECT_ERROR = None
@@ -88,7 +87,6 @@
             if exc.status == 403:
                 _cred_sub_check(s3client.connection_data)
     except Exception as exc:
-        logging.exception(exc)
         S3_CAN_CONNECT_ERROR = str(exc)
     except keystoneclient.exceptions.Unauthorized:
         S3_CAN_CONNECT_ERROR = "AWS credentials not set," +\