This allows reuse of the blocking code as well as having multiple proxies to the same token. Blocks the calling thread if would block. Blocks the calling thread if would block.
Calls renew on the token.
This is implemented as thread-specific data. I strongly recommend that this not be used unless you really know what you're doing. I use this in the Token Server, and it caused many headaches. Return the name of the token. The name must uniquely identify a token.