It turns out the Linux server has a bug in its implementation of
supattr_exclcreat; it returns the set of all attributes, whether
or not they are supported by minor version 1.
In order to avoid a regression, we therefore apply the supported_attrs
as a mask on top of whatever the server sent us.
Reported-by: Anna Schumaker <Anna.Schumaker@Netapp.com> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>