[Samba 4] Failure to copy file w/ streams to an smbd on a fs with no stream support

[Andrew Tridgell]

Marc,

As discussed on irc, the file I sent you didn't have any special
properties, but the reason you get the error is that the pvfs backend
was detecting xattrs in the kernel, and telling the client it has
stream support at connection time. The pvfs backend then detected that
xattrs were in fact disabled in the filesystem once you did a
operation that needed them, and gave an error to the client.

I've committed a fix that should trigger the xattr detection at
connection time, so hopefully the client will know right from the
start that the server does not supports streams if the filesystem
doesn't support them.

Cheers, Tridge