Deprecate s3_token middleware

The s3_token middleware is now deprecated in favor of the s3_token
middleware in python-keystoneclient.

bp s3-token-to-keystoneclient
bp deprecated-as-of-icehouse

Change-Id: Ic39b0d444124020ca52e1621d640fdd512cc8df4
Merge "Deprecate s3_token middleware"