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
1 file changed