Fix V3 credential behavior, documentation

Fixing V3 credential behavior so that contradicting parameter combinations
do not result in unpredictable behavior.  Updating accounts.yaml.sample
file to reference the correct location of the credentials
classes and to describe the updated behavior of Identity V3 attributes.

Change-Id: I29efe778afcb1e4a55dffd6a8ed8212d62a4dd15
3 files changed