console: introduce a new exception InvalidToken
console: introduce a new exception InvalidToken

Introduces a new exception InvalidToken used when an effectively
invalid token has be sent to a console proxy.
Updates the code to take advantage of this new one.

Change-Id: I9eb18541847e0ce22d5a449268876043ed8eb3a1

openstack/oslo.versionedobjects,citrix-openstack-build/oslo.versionedobjects