Previously, when a password change occured in ironic,
the session would not be invalidated, and this, in theory,
could lead to all sorts of issues with the old password
still being re-used for authentication.
In a large environment where credentials for BMCs may not
be centralized, this can quickly lead to repeated account
lockout experiences for the BMC service account.
Anyhow, now we consider it in tracking the sessions, so
when the saved password is changed, a new session is
established, and the old session is eventually expired out
of the cache.
Change-Id: I49e1907b89a9096aa043424b205e7bd390ed1a2f
c2ba869040