return a new session even if there are no cache devices currently enabled. Also, changed DeactivateEntry() to bind non-doomed entries if necessary to allow the storage of meta-data-only entries, such as HTTP redirects. r=sfraser, sr=darin. git-svn-id: svn://10.0.0.236/trunk@105739 18797224-902f-48f8-a5cc-f745e15eee43