Remove extra MANAGE caveat for file upload 

As reported by Paul, for FTS transfers the list of caveats requested to the destination contains twice the MANAGE caveat. FTS includes it in the list and the x509-scitokens-issuer adds it again at

https://github.com/scitokens/x509-scitokens-issuer/blob/master/src/x509_token_issuer.cpp#L112

Can we remove this duplicate? or maybe add it if it's not already there?