Revert "Add-in some re-auth logic when using os_cache"

This patch didn't do what it was supposed to do, make os_cache work. Instead it just adds complexity, so just remove it.

This reverts commit 8eed73ce20ff0808d350fc9af66d6ba55ebda017.

Change-Id: I7c118cbf8d8e2218e198d603f1984a9de18266c4
Document and make OS_CACHE work

Before the --os-no-cache option logic would overwrite any value set in env['OS_CACHE'].
Since os-no-cache  is deprecated, and also the default value, just remove it.
Also update the help message for --os-cache to mention the environment variable.

Change-Id: Ie2569d5cdf0f12f3a29e9a6f20faef75956d2209
Make os-cache retry on an invalid token

client.authenticate doesn't actually do any rest calls if a token is present,
it just assumes the token is valid.  Instead re-authentication is done if the
request raises an Unauthorized exception, at which point we want to
unauthenticate (delete the token from in-memory) and overwrite the old token
in the keyring. Also if a password is present allways pass it into the client
so re-authentication is possible during _cs_request.

Change-Id: I86d0356d5685ffa802f1bdc97e33727ff2dd075e
Remove deprecated NOVA_RAX_AUTH

NOVA_RAX_AUTH has been deprecated in favor of a generic pluggable auth,
which in this case rackspace users can set OS_AUTH_SYSTEM=rackspace

Fixes bug 966329

Change-Id: Ie55fc36a0ac1cba61efa8bdd2f20809530d3365f
Merge "Remove deprecated NOVA_RAX_AUTH"
Merge "Revert "Add-in some re-auth logic when using os_cache""
Merge "Document and make OS_CACHE work"
Merge "Make os-cache retry on an invalid token"