Do not log the full session ID

According to our logging guidelines we should not log sensitive data:
https://wiki.openstack.org/wiki/Security/Guidelines/logging_guidelines

This patch changes all log statements to log only the last 5 characters
of the session ID, so we can still have something for debugging
purposes.

Change-Id: I0e524eeca9ad3417a71039681ca1d64d589346fe
Merge "Do not log the full session ID"