Log specific error message from RetriableConnectionFailure
Log specific error message from RetriableConnectionFailure

There are more than one error from keystoneauth that can match
RetriableConnectionFailure. We retry on all of them, but logging the
whole message can be useful for debugging.

Change-Id: I2fd3bf62a3a755281d34ff5d3624b835281604fb

dtroyer/python-openstacksdk,stackforge/python-openstacksdk,openstack/python-openstacksdk,openstack-infra/shade,openstack/python-openstacksdk,dtroyer/python-openstacksdk,openstack-infra/shade,stackforge/python-openstacksdk