fs.s3a.authoritative.path should support multiple FS URIs

(This may have worked until we did recent changes to s3a path qualification)

fs.s3a.authoritative.path was intended to support not just a list of paths, but a list of URIs, so that you could explicitly list those paths which were authoritative in specific buckets.

Parsing of the list in an FS instance must therefore discard all which are of different URI authorities