Some changes to make keystoneclient more backwards compatible
by disabling key caching by default.
This patch renames the CLI option for when to use the
auth token cache to --os-cache and sets it to False by default.
It also changes the ENV variable to OS_CACHE (instead of OS_NO_CACHE).
Change-Id: I6e549feec6ee7500e398a1eceb5bb44cd7d40347