stream-clone: bail-out earlier if stream clone is not requested
The `canperformstreamclone` function is bit messy. However it seems clearer to
me to check if a stream-clone have been requested by the client or the server
at all, before checking if a compatible protocol can be negotiated with the
server.
So I am doing some gratuitous movement so reorder conditional.
[workspace]
members = ["hg-core", "hg-cpython", "rhg"]
exclude = ["chg", "hgcli"]